You can actually already Pin in DarwinMail :) There's a lever on the right of the search bar (from your mail inbox). Click that to show all your Pinned emails.
You can also hover over any mail to show its actions. The Pin is second from the left. Next to the star ;)
as for bundling/and one-click archiving bundles.. that's been requested a few times today and I will be working on it asap. https://www.darwinmail.app/feedback.php
If you have any more requests let me know or post them at the above link!
Should I add a feature spotlight for Pinning to the homepage though? I don't think it's clear that Darwin Mail supports Pinning as of now!
Thank you so much for your feedback :) This kind of feedback is what makes products great!
However, I'm going to merge that with DarwinMail's Trello board soon and make the whole thing public :)
I will also allow upvoting, comments and user-created feedback and suggestions!