First thread! Tell us which features you’d like to see in Substack, or ask us feature-related questions. (Please, no support questions – send those to support@substack.com.)
Would like to be able to "group" subscriptions. I subscribe to like 40 different Substacks, and right now they're all in one "bucket." It would be nice to be able to have them in separate buckets. There are some I want to read every day and some I want to go back to and savor.
Great idea! I'd like to build off this and add how it would be great to easily Pinterest pin this too with content generator's convenient ability to add their own photo with title for easy referencing. Bonus would be to link that to a free stock photo stockpile readily at hand.
2nd this. I would actually prefer zero formatting or only via markdown for max simplicity so I can focus on a post instead of how it looks. There's a happy medium though
ha, too funny. What other formatting options are Not Now Not Ever? I've been wondering what might be coming vs. what is intentionally left out. Personally I'd love things like image alignment and highlighted text.
Agree. I get Chris's stance on this but over wished for the centering option when writing a bit of text before it after a subscriber button to and get people to subscribe. A short sentence looks funny left aligned right above a centered subscribe button.
I've tweeted at you guys about this before (and also talked to Hamish about it), but just reiterating my longing for an iOS app so I can write on the go!
I would like to be able to post a single post in two languages, so the readers would automatically get it sent or see it online in their language automatically either:
I also would find this feature incredibly valuable. Adding language options would majorly expand my reader base and the idea of creating another newsletter seems unwieldy.
Any updates on this? At the moment I am writing the newsletter in both languages in the same post, with languages flags. It's the easiest way at the moment for the reader, who does not have to subscribe to different sections and click too many links. Another option was indeed, to add a link to the Italian version in the original version, a post nobody gets via email but that everyone can get access to via a link to the original English newsletter. Which one is better? My channel is free for everyone atm, but I guess If I ever turn on a paywall, it will get a lot more complicated.. thoughts?
Anchors. So, we can click to another spot in our newsletters or direct people straight to that spot when we reference something in a newsletter in another social medium. (At least 'anchors' is what they used to be called when I was hand-coding newsletters many years ago...
Quick note: we have had so many people asking for this that we are going to have to make a more automatic version, hopefully within the next couple weeks.
For all that have written in to support: thanks for your patience!
1. A way to gift a paid subscription for a specific duration to an email address via API. This would make it easier for me to sync my Patreon patrons over to Substack as I transition people over and eventually deprecate Patreon use.
2. Zapier support for new subscriptions so I can also invite them to other places (like my Discord community).
3. Multiple tiers of subscription, and a way to tag subscribers to a tier. I'm using coupons right now to create a $1 tier and a $5 tier, but there's no way to send things only to the $5 tier subscribers. There are also use cases where I might want two $1 tiers for different areas of interest, so being able to segment my subscribers by a supplied tag or group would be great too.
4. Plus-100 to image resizing so I don't have to re-crop tall images to not take up the entire screen.
These are not super urgent request, just the ones that came to mind. Overall, loving Substack and also love that you are able to say no to feature requests to keep things minimal.
I'm definitely seeking a way to smoothly transition patrons over before I launch my Substack. I'm struggling to find a simple way, as my Patreon was built for me with more tiers (10) than I would have chosen (3).
seconded on multiple tiers of subscription-- I have a $100 a month investing community--a $9.95 trial for 30 or 60 days that converts to monthly/yearly REALLY works for me! I would transfer over with that functionality
Just starting out but I agree with the calls for more design control, image placement, font size/style options, etc. The ability to have a caption/attribution under an image would also be nice. Thanks.
I'm a Zen poet and also an insight writer, journalling on silence. I'd love to see what you do. I haven't founded my Substack yet, but am working on it. What's your URL Phil?
I'm sure this is on the radar but to add to your comment, stats/analytics on opening rates down to individual users. Then there's lots of opportunity for AI to pick the best recipients, subject lines, and times to send to maximize readership.
Can the individual data Hamish just mentioned be exported?
If so you can cross-reference it with the mailing list export and easily create an heuristic for sending it to each individual user's prefered reading time (by prefered I mean the time they actually read it, regardless of whatever think is the best time to receive it).
I do think this would be cool. Our goal would probably be to give you more control over the brand and feel, while still keeping the layout & functionality pretty standard.
Good to read. This is actually my current deal breaker to move from Mailchimp. Your design is slick but I want to be able to differentiate a bit. (Any chance on a text editor flipped to from the wysiwyg?)
because all of our newsletters get archived, i would love more layout options to show them. perhaps by topic or just the ability to personalize it a bit more.
I would love to see an email "autoresponder" feature where you can select a number of archived posts that get sent to new subscribers in any order you choose at a preset interval (e.g., daily, weekly, etc.). This could be positioned as a "free email course" or series to encourage people to sign up for your list and introduce them to your content in a predetermined manner. Great product! Keep up the good work!
Oh, I like this idea... kind of like a series of welcome posts, but instead of going out all at once, they get sent to subscribers at set periods after they subscribe... is that what you have in mind?
I will second the ask for tagging, both tagging at an overall mailing list level and tagging on a per-post basis. Right now the only stuff that comes up in search seems to be the stuff that's put in the one-line descriptions in settings. My posts will never ever show up on the front page, but if I write about some obscure topic and someone specifically searches for that topic, I'd like them to be able to find what I wrote.
A series feature where I can string a bunch of posts into a reading sequence, with all sequence trailheads listed in a series index. Reverse chronology is a bitch. On my wordpress blog, ribbonfarm.com, I use a series plugin for doing this. Since I have many parallel, intertwined threads going on my 2 lists, gives new readers a way to catch up instead of facing an intimidating archives-moat. Especially valuable for those of us who like to gradually build on past issues.
Option for Image selection and attribution from sourced articles. Specifically, pull and display/format image(s) from source article and put attribution in editable text box.
Oh, here's a super minor one for everyone else that's mostly just important for me because I write about books: in the emails, text that is bolded, italicized, and hyperlinked just shows up as italicized and underlined, but not bold. Would love for it to display as all three, though this could also be an email client issue.
It would be good if the video on click in the email client went to substack platform (web) as opposed to youtube / vimeo .... keep people on the newsletter .
Would love 1-2 other static website pages other than the About page -- I needed one to post my privacy and data collection policy and had to host it elsewhere. Also, seconding all the comments requesting various customizable promo codes.
Finally, I've found a lot of people don't really realize that this is a newsletter you can subscribe to when they're linked to a post, especially people unfamiliar with Substack. Not sure what a fix would look like, but would love it if it was somehow clearer what subscribing meant -- maybe some sort of customizable call to action on free web posts above the subscribe button, succinctly explaining that this is a newsletter about XYZ, sign up for free updates or subscribe and pay for all posts. I find I really have to explain what it is to people right now before I can get them to subscribe, which defeats the utility of free posts that get a lot of clicks outside my own social media channels, places where I can't highlight to people that it's a newsletter.
In addition to the welcome emails, I would like to be able to send certain emails with a trigger of my choosing. For example, send a 'thanks for reading' email after 10 emails opened.
Also, while I appreciate you guys seeking user feedback, I kinda like how you’re product-driven and opinionated so I’d like to see you continue that to the tune of say 80% of the roadmap and listen to us only 20%. I’m wary of this turning into Homer Simpson’s car https://simpsons.fandom.com/wiki/The_Homer
If this wasn't mentionned before, would love the ability to bulk select subscribers. Mostly for list cleaning / list management / export or copy paste.
Love the platform overall & appreciate how you've put so much thought into keeping it streamlined.
-One suggestion I'd like to echo would be to allow for a little more site customization to make branding (especially for those who have migrated from other platforms) more seamless. (Things like web font choices, etc.).
-Second thing would be pagination of email openers/subscribers, etc - clicking to view details about a subscriber returns you to the top of the list right now.
The ability to create a simple one link, a few lines email from an article. something like Buffer/hootsuite for newsletters. I'd like to send quick updates to my subscribers or clue them into something really quickly. If I can send an email as quickly as I can tweet. That'd be great. LIke breaking updates since my newsletter is all about industry news.
Yes, a broadcast function to paid, all subs, individual subs, or other subscriber segmentation/filters as is possible. For quick/short updates not needing a full issue.
Is there a way to (as a publication) turn off email receipts that subscribers are sent for recurring subscriptions? I feel turning them off by default would help keep churn down, especially for the monthly subscribers.
Love the splash page but would love a way to customize it a bit more. Have a few different ways to ask for subscriptions. First name last name would be good to have as well.
A call to action to subscribe automatically added to the end of each free post. I share free posts to grow my list, but it seems like a lot of people are reading without subscribing to the free list. Creating a more prominent reminder could be great.
First I would just like to say thank you for creating a great platform. Really great job!!
I would like to see two things:
Accept Cryptocurrency you can use something like Coinbase to do this.
I am still a growing newsletter but would be cool to have some of the lower subscribed newsletters on the front page. Kind of like what Bandcamp does to feature interesting bands.
Again these are just requests, something I would like to see over time.
I'd love to have all the features I have on my laptop available on mobile (iOS) Things like auto embedding of videos from links etc. A wordcound as I write would also be cool. I'd also like to be able to export all my newsletters as a book. ;-)
You can do that already. It is a faff having to encode a Wav to an mp3 (that could happen server side) but you just need to make sure that your podcast sits in Dropbox or iCloud etc. I use Backpack Studio to make my podcasts.
Got it. Interesting one. It's already possible with a bit of a workaround – after each post has been sent, you can go back into it, click on Settings, and then click on "Unpublish".
You also can do this by selecting "Only free" when you're choosing how to send out an email (from Everyone, Paid Only, Only Free). Those will send out to your free list, but won't show up in your archive on your substack site.
A web clipper and iOS extension to save articles for later newslettering
Noted!
Would like to be able to "group" subscriptions. I subscribe to like 40 different Substacks, and right now they're all in one "bucket." It would be nice to be able to have them in separate buckets. There are some I want to read every day and some I want to go back to and savor.
There are some tools for the purpose such as Evernote Web Clipper, Notion Web Clipper, Glasp, etc
Or Readwise/Reader. You can just forward the substack email to your special Readwise address and bingo.
Great idea! I'd like to build off this and add how it would be great to easily Pinterest pin this too with content generator's convenient ability to add their own photo with title for easy referencing. Bonus would be to link that to a free stock photo stockpile readily at hand.
Oooh, I would love more formatting options. Center text alignment, sans-serif / serif typeface, just a few more options would be swell
Chris Best will never allow centering...
I am the evil grinch of left alignment!
Less is more in formatting. I like the simple approach. Fewer decisions! I an focus on content.
2nd this. I would actually prefer zero formatting or only via markdown for max simplicity so I can focus on a post instead of how it looks. There's a happy medium though
Makes sense. The editor right now is basically everything supported in markdown + a few goodies
but i just wanna do captions for photos will you make an exception!?
I appreciate this, but you'll be alienating just about the entire poetry community with this stance.
ha, too funny. What other formatting options are Not Now Not Ever? I've been wondering what might be coming vs. what is intentionally left out. Personally I'd love things like image alignment and highlighted text.
Yes, highlighted text please!
maybe you could fork the code - and give the world the fork that supports centering and Chris Best the other fork?
Agree. I get Chris's stance on this but over wished for the centering option when writing a bit of text before it after a subscriber button to and get people to subscribe. A short sentence looks funny left aligned right above a centered subscribe button.
Seconded!
Word!
I've tweeted at you guys about this before (and also talked to Hamish about it), but just reiterating my longing for an iOS app so I can write on the go!
I would also love this.
plus one to this
me too!
And an Android one too. :)
Yes, please!
or maybe extensions so for example - write to Drafts and publish?
I would like to be able to post a single post in two languages, so the readers would automatically get it sent or see it online in their language automatically either:
* based on preference
* based on browser setting
I've put this link on https://www.reddit.com/r/Substack/comments/xoj2o2/bilingual_posts/ as well.
I also would find this feature incredibly valuable. Adding language options would majorly expand my reader base and the idea of creating another newsletter seems unwieldy.
Any updates on this? At the moment I am writing the newsletter in both languages in the same post, with languages flags. It's the easiest way at the moment for the reader, who does not have to subscribe to different sections and click too many links. Another option was indeed, to add a link to the Italian version in the original version, a post nobody gets via email but that everyone can get access to via a link to the original English newsletter. Which one is better? My channel is free for everyone atm, but I guess If I ever turn on a paywall, it will get a lot more complicated.. thoughts?
Anchors. So, we can click to another spot in our newsletters or direct people straight to that spot when we reference something in a newsletter in another social medium. (At least 'anchors' is what they used to be called when I was hand-coding newsletters many years ago...
Seconded!
maybe automatically generated for headings?
thirded
+1
A newsletter signup widget I can host on my own website! And +1 to more design customization options
Write in to ask for an embeddable subscribe form and we'll hook you up. support@substack.com
Quick note: we have had so many people asking for this that we are going to have to make a more automatic version, hopefully within the next couple weeks.
For all that have written in to support: thanks for your patience!
Great to hear!
The widget idea is great
It'd be great if we could preview the URL for scheduled posts, so I could also pre-schedule social shares for when public posts go live.
Custom domains please!
+1
I second that.
I third that.
+1
1. A way to gift a paid subscription for a specific duration to an email address via API. This would make it easier for me to sync my Patreon patrons over to Substack as I transition people over and eventually deprecate Patreon use.
2. Zapier support for new subscriptions so I can also invite them to other places (like my Discord community).
3. Multiple tiers of subscription, and a way to tag subscribers to a tier. I'm using coupons right now to create a $1 tier and a $5 tier, but there's no way to send things only to the $5 tier subscribers. There are also use cases where I might want two $1 tiers for different areas of interest, so being able to segment my subscribers by a supplied tag or group would be great too.
4. Plus-100 to image resizing so I don't have to re-crop tall images to not take up the entire screen.
These are not super urgent request, just the ones that came to mind. Overall, loving Substack and also love that you are able to say no to feature requests to keep things minimal.
Thanks Buster. Some great stuff here. Email support about point 1? We might be able to help you out there...
I'm definitely seeking a way to smoothly transition patrons over before I launch my Substack. I'm struggling to find a simple way, as my Patreon was built for me with more tiers (10) than I would have chosen (3).
seconded on multiple tiers of subscription-- I have a $100 a month investing community--a $9.95 trial for 30 or 60 days that converts to monthly/yearly REALLY works for me! I would transfer over with that functionality
+1 on 3.
+1 on 4.
+1 on 4.
Absolutely agree with Zapier support!
A homepage / reader (think Feedly, Google Reader, etc) where I'd be able to read issues from Substacks I follow
100%. I have started losing them in my inbox but I'd love to be able to go find them all in one place.
+1
Gmail is particularly nefarious as it inconsistently sorts substacks into random inboxes like promotions or updates or even social!
THIS!
more on-site analytics; specifically bounce rate & time on site.
Definitely on our to-do list.
In the mean time: we just quietly shipped support for Facebook, Google, and Twitter pixels in case that helps. Its in the settings page.
Ohhh, good to know, I'd love Google Analytics insights. Will set this up.
Maybe the ability to embed a google analytics code ?
That would solve a lot of challenges in knowing better and understanding my audiences
Now possible – just added to the settings page.
Thank you, everyone, for participating in this thread. We're checking out for the day. We'll do this again soon!
instagram embeds!
We now support basic Instagram embeds. More to come, but feedback welcome.
Just starting out but I agree with the calls for more design control, image placement, font size/style options, etc. The ability to have a caption/attribution under an image would also be nice. Thanks.
Seconded on all!
i 'fourthed' a related comment just now - so I guess this would be 'sixthed' ?
+1 for all ~ Thanks
Changing image size without using external tools :)
Insane!
Seconded!
Tags or categories? Interest communities? Like, who else is mailing poetry and can we help each other out somehow?
This might be of interest in the meantime: https://substack.com/search
I'm a Zen poet and also an insight writer, journalling on silence. I'd love to see what you do. I haven't founded my Substack yet, but am working on it. What's your URL Phil?
Cool! I'm at philwells.substack.com - let me know when yours is all set up!
Definitely would like to see more social affordances. Side notes a la Medium, for example.
The ability to create segments within an email list. (For example, "people who regularly open" or "former paid subscribers.")
I'm sure this is on the radar but to add to your comment, stats/analytics on opening rates down to individual users. Then there's lots of opportunity for AI to pick the best recipients, subject lines, and times to send to maximize readership.
We do already show individual subscriber stats. Check out the "Subscribers" tab in your dashboard and then scroll down to the (searchable) list.
Yeah sorry, I meant do the cool AI thing sometime ;)
Can the individual data Hamish just mentioned be exported?
If so you can cross-reference it with the mailing list export and easily create an heuristic for sending it to each individual user's prefered reading time (by prefered I mean the time they actually read it, regardless of whatever think is the best time to receive it).
Understanding when people are reading/when the best time and day to send would be amazing.
oh yes PLEASE!
+1 for list segments
I'd like to find a more prominent way for my name to be highlighted as the writer of the newsletter.
More ways to customize email templates/layout. Would love to differentiate more from other newsletters :).
I do think this would be cool. Our goal would probably be to give you more control over the brand and feel, while still keeping the layout & functionality pretty standard.
Good to read. This is actually my current deal breaker to move from Mailchimp. Your design is slick but I want to be able to differentiate a bit. (Any chance on a text editor flipped to from the wysiwyg?)
Fourthed - what stops support of at least some HTML?
"Thirded"!
Seconded!
+1
because all of our newsletters get archived, i would love more layout options to show them. perhaps by topic or just the ability to personalize it a bit more.
I would love to see an email "autoresponder" feature where you can select a number of archived posts that get sent to new subscribers in any order you choose at a preset interval (e.g., daily, weekly, etc.). This could be positioned as a "free email course" or series to encourage people to sign up for your list and introduce them to your content in a predetermined manner. Great product! Keep up the good work!
Oh, I like this idea... kind of like a series of welcome posts, but instead of going out all at once, they get sent to subscribers at set periods after they subscribe... is that what you have in mind?
Yes, exactly. This is the only feature preventing me from moving completely off of Mailchimp or a similar email marketing service.
+100 Hugely helpful for writers with serialized publications ~ Wide variety of potential applications.
Easy intuitive drop down to insert links to previous articles we wrote in Substack and tagging for articles to make search better.
I will second the ask for tagging, both tagging at an overall mailing list level and tagging on a per-post basis. Right now the only stuff that comes up in search seems to be the stuff that's put in the one-line descriptions in settings. My posts will never ever show up on the front page, but if I write about some obscure topic and someone specifically searches for that topic, I'd like them to be able to find what I wrote.
+1 for both! Great suggestions
A series feature where I can string a bunch of posts into a reading sequence, with all sequence trailheads listed in a series index. Reverse chronology is a bitch. On my wordpress blog, ribbonfarm.com, I use a series plugin for doing this. Since I have many parallel, intertwined threads going on my 2 lists, gives new readers a way to catch up instead of facing an intimidating archives-moat. Especially valuable for those of us who like to gradually build on past issues.
I need this.
+1
Yes, yes, yes!
Option for Image selection and attribution from sourced articles. Specifically, pull and display/format image(s) from source article and put attribution in editable text box.
YES - would love image captions/attribution
+1
Oh, here's a super minor one for everyone else that's mostly just important for me because I write about books: in the emails, text that is bolded, italicized, and hyperlinked just shows up as italicized and underlined, but not bold. Would love for it to display as all three, though this could also be an email client issue.
Oh thanks for this. We'll look into it...
Seconded!
also the ability to embed video into a newsletter without having to host it elsewhere first
One day...
It would be good if the video on click in the email client went to substack platform (web) as opposed to youtube / vimeo .... keep people on the newsletter .
seconded
Would love 1-2 other static website pages other than the About page -- I needed one to post my privacy and data collection policy and had to host it elsewhere. Also, seconding all the comments requesting various customizable promo codes.
Finally, I've found a lot of people don't really realize that this is a newsletter you can subscribe to when they're linked to a post, especially people unfamiliar with Substack. Not sure what a fix would look like, but would love it if it was somehow clearer what subscribing meant -- maybe some sort of customizable call to action on free web posts above the subscribe button, succinctly explaining that this is a newsletter about XYZ, sign up for free updates or subscribe and pay for all posts. I find I really have to explain what it is to people right now before I can get them to subscribe, which defeats the utility of free posts that get a lot of clicks outside my own social media channels, places where I can't highlight to people that it's a newsletter.
+1 for more user-designed static pages (Example: "Best Of" etc.)
In addition to the welcome emails, I would like to be able to send certain emails with a trigger of my choosing. For example, send a 'thanks for reading' email after 10 emails opened.
+1
Also, while I appreciate you guys seeking user feedback, I kinda like how you’re product-driven and opinionated so I’d like to see you continue that to the tune of say 80% of the roadmap and listen to us only 20%. I’m wary of this turning into Homer Simpson’s car https://simpsons.fandom.com/wiki/The_Homer
With you all the way on this!
Agree, great to keep it clean. But, I want a car like Homer’s!
Ability to set special offer priced trial subscriptions--One or Two Month Trial $1--then conversion to one year full price
Some writers use their own domains. When will custom domains be publicly available?
If this wasn't mentionned before, would love the ability to bulk select subscribers. Mostly for list cleaning / list management / export or copy paste.
+1
This might have been said, but more unified analytics. See all stats on one page.
Coloured hyperlinks
Thank you! Love this platform and how easy it is to get started. A couple of my feedbacks:
1. Easier ability to see names of authors associated with newsletters
2. More analytics drill-downs: I.e. the ability to see where traffic is coming from day by day
3. Ability to email specific groups; i.e. people who haven't ever read - prompt them to unsubscribe if they want to
4. Breakdown of yearly/monthly recurring revenue
Seconded!
Custom Domains!
Love the platform overall & appreciate how you've put so much thought into keeping it streamlined.
-One suggestion I'd like to echo would be to allow for a little more site customization to make branding (especially for those who have migrated from other platforms) more seamless. (Things like web font choices, etc.).
-Second thing would be pagination of email openers/subscribers, etc - clicking to view details about a subscriber returns you to the top of the list right now.
Thanks again for all you're doing! Cheers
-A toggle for 'Newsletters' and 'Podcasts' on the landing page so that it's easily filterable
-Detailed information on podcast metrics (similar to Libsyn)
The ability to create a simple one link, a few lines email from an article. something like Buffer/hootsuite for newsletters. I'd like to send quick updates to my subscribers or clue them into something really quickly. If I can send an email as quickly as I can tweet. That'd be great. LIke breaking updates since my newsletter is all about industry news.
Yes, a broadcast function to paid, all subs, individual subs, or other subscriber segmentation/filters as is possible. For quick/short updates not needing a full issue.
+1
Is there a way to (as a publication) turn off email receipts that subscribers are sent for recurring subscriptions? I feel turning them off by default would help keep churn down, especially for the monthly subscribers.
Love the splash page but would love a way to customize it a bit more. Have a few different ways to ask for subscriptions. First name last name would be good to have as well.
Discount codes or direct link to paid subscription service for social media use?
We'll do more with coupons in the not-too-distant future.
That's great. I think I could convert more from Twitter if they had a direct link to paid instead of the welcome page sign up.
Also, I can't seem to offer a discounts through free emails anymore?
We took those out for now because they weren't quite right, but coupons will make a comeback in other forms.
Thank you.
+1 for discount codes! Would also love coupon codes that gave some free X amount of time, where we could set expiration.
instagram embeds!
Second!
Coloured hyperlinks
Seconded!
+1
For podcasting, the ability to pause/restart recording and record interviews with others similar to Anchors capes
Would be very cool.
Tell the founders!! ; )
They'd never listen to me.
I wish twitter embeds with videos would include the video and I would like 5000 more people to pay for my newsletter.
If we solve the former, the latter will surely take care of itself.
A call to action to subscribe automatically added to the end of each free post. I share free posts to grow my list, but it seems like a lot of people are reading without subscribing to the free list. Creating a more prominent reminder could be great.
First I would just like to say thank you for creating a great platform. Really great job!!
I would like to see two things:
Accept Cryptocurrency you can use something like Coinbase to do this.
I am still a growing newsletter but would be cool to have some of the lower subscribed newsletters on the front page. Kind of like what Bandcamp does to feature interesting bands.
Again these are just requests, something I would like to see over time.
Thanks for the kind words and good feedback!
I'd love to have all the features I have on my laptop available on mobile (iOS) Things like auto embedding of videos from links etc. A wordcound as I write would also be cool. I'd also like to be able to export all my newsletters as a book. ;-)
Yea would be cool to create podcast from iPad
You can do that already. It is a faff having to encode a Wav to an mp3 (that could happen server side) but you just need to make sure that your podcast sits in Dropbox or iCloud etc. I use Backpack Studio to make my podcasts.
The ability to send free newsletters that don’t appear on the username.substack.com homepage
Do you mean that don't show up on substack.com?
Yes. So that people have to subscribe (even for free) to recieve any information
Got it. Interesting one. It's already possible with a bit of a workaround – after each post has been sent, you can go back into it, click on Settings, and then click on "Unpublish".
You also can do this by selecting "Only free" when you're choosing how to send out an email (from Everyone, Paid Only, Only Free). Those will send out to your free list, but won't show up in your archive on your substack site.