If I can't be bothered to use another workspace for Gimp, then I'll open it as a stacked window in StumpWM. So no fighting over space.
If you seriously end up with 5+ GIMP instances and 5+ projects, then I have to say: there is no way you work on that many projects at once. If you do, then that sounds more like a workflow problem.
I usually only have one, maybe 2 projects open, and a browser or two somewhere, maybe a terminal if I need a non-Emacs terminal. If you got 3-4-5-6 projects going at the same time that really is a project management problem I'd wager.
Might also be that I just have tabs or "workspaces" in my Emacs.
But I just can't see the advantage of the scrolling to just plain workspaces. The scrolling to me just adds one more indirection of having to remember where something is. It adds a new level to the navigation tree.
We can probably end that then, because you saw MY point. Whatever that means :D
Tried Niri before, but it seemed more to adhere to fancy animations than actual improvements.