Some apps, like Slack, have a Menu Bar. (File, Edit, View, etc.). In Pop_OS, pressing Alt, shows and hides said menu (in most apps, the behavior is somewhat inconsistent); for the most part, this is all I need, since I usually hide the menu, and only enable it when I need (which is rare, but it happens).
On Elementary (JUNO), I see the menu in slack, but it has no shortcut associated, so I don't know how to bring it back once gone:
Any hints? :)