Hi! While certainly possible I have no (current) plans to add this functionality (but I’d appreciate any PR’s!)

But I think you could make this work without the app itself supporting by writing a plist key for the app, and then setting up a global shortcut that opens it.

How to hide a dock icon: https://apple.stackexchange.com/a/207944

And example of how to set up a shortcut to open any app: https://superuser.com/a/1553303

Thanks for the answer.
I'd love to contribute a PR, but this is completely out of my area of expertise :-)

As for the workarounds - down in the first link you'll see this: https://apple.stackexchange.com/a/440941
(TL;DR: not possible anymore)
In which case, I'll just continue to use FMail (v1), which does that.

Thanks!

Ah yes sorry about that, missed it. I assume you had already tried it!

But feel free to keep this issue open as a feature request and I might get inspired to add it some day

That's great, thanks 🙂