OK, so here is the deal.
I work on games and commission work and usually have a lot of files open. Also my memory is bad and I hate finding stuff again, so I run on “Load previous session” a lot, it’s the most needed feature for me.
This might be a bit niche though, but I’d love to save a current session and then load it again another time.
Also having multiple sessions would be nice, so I could decide to load up what I need for commissions or for game development.
Also knowing that even if I just shut down the program, without loading anything, that mt session is save, would be nice.
While at it, tab groups might be pretty neat too, but I know I am asking a lot already.
But yeah, just being able to save what files are open, in a session-save file would be awesome. Then a menu to load entire sessions in.
I think I understand the problem behind 
But some detail questions would come up:
Once you saved the currently opened files as some session.
Now you add a new file and close PM.
Would this update that session file automatically?
How would the “auto” session that is used today generally work with such individual sessions?
I assume that instead of the “auto” session that it uses today, it would just load the session file you previously used?
Would it maybe be even enough to just enable loading of all files in a folder?
So that you manage your files on that level? This would of course only make sense if you always want to open all files in a folder.
Can you give an example about how tab groups would work? Is there a software that does that well for you?
Thinking about this, I think this might be best:
You have an auto-session, like you do now. This auto-session gets loaded up on start (no need to click “Load previous session”, as it automatically restores, similar to Firefox and other browsers).
Then you can also save snapshots. Pretty much what is open right now, which you can then load later.
These won’t be edited, when you open new files, that goes to the auto-session.
Also when you load a session file, it pretty much just resets the auto-session.
I don’t think loading everything from a folder would work. At least I tend to sort things a specific way, that would create a mess then.
But having a snapshot option and sessions auto-restore would help a lot.
And for the grouping, I honestly have not much experience with software there.
How I imagine it, is that there could be additional tabs. These then expand, when you click on them.
These tabs could also be named, so I could have “Game dev - enemies” and “Game dev - Mockups” as tabs, that expand into tabs I put into them. Otherwise they are collapsed.
Honestly. this sounds more like a mess than it’s worse though. The idea is to keep the tabs cleaner, but I feel it might make it messier.