I'll write quite short answers to save time and space.
I suspect that is by-design. It at least makes sense to me. (It's rare that you'd want to toggle one off and the other on, IMO.) You might be able to use @ifset to create a button which really does toggle both. If you need that (and aren't just reporting it as something you noticed) and need help setting it up, let us know. (Please start a new thread for it, though.)
Go FOLDERCONTENT is only intended to be used with fixed paths, not things like {sourcepath}.
Viewers that handle keyboard input will take over (most) hotkeys, as the hotkeys may have meaning within the viewer.
If it's something you need, and you link your account, we'll add it to the request list.
Noted.
Does it scroll if you hover over the arrows themselves? I think that's how it works, but that's just from memory and not double-checked.
That's probably by-design, although I haven't confirmed it yet.
Seems like something is wrong if you are encountering those things often enough for it to matter. Are you using a really small screen with a configuration design for a much larger one, or something?
If the problem is lots of context menu items from 3rd party shell extensions, there are ways of hiding them or organising them into sub-menus which will be much better than having to scroll toolbars and menus all the time.
You can use // to comment out lines already.
Once a tab-group is open, you just have a bunch of tabs open. There's no record that they came from a particular group. I guess we could add that. What kind of situation would you use it in, where you wouldn't just close all tabs & open a new group (or groups) instead?