[notafox]

Forget about UI, just use CLI

    ./firefox -CreateProfile "profile-name /home/user/.mozilla/firefox/profile-path/"

    ./firefox -profile "/home/user/.mozilla/firefox/profile-path/"

Create a separate icon for each profile and forget about:profiles interface.

Disclaimer: I don't use macOS, but I'm sure it's similar to Linux in that regard. You'll need to change paths, of course.

[celsoazevedo]

That's great for part of HN users, just not for most Firefox users. I guess that's they already had the old interface and are making it more user friendly with the new UI :-)