How many free Library slots do you have? Each library slot (8 total) can have 256 custom arpeggios as well. If you use all library slots + the user area, you can have 2,304 total custom ARPs.

Even if you have a Library installed now - you could backup your user area - clear your user area - then import your Library into the user area, add a bunch of user ARPs until your user area is filled with 256 ARPs , then save it back as a Library (X7L) and load the new Library. Deleting the original library. Fill up as many libraries as you want with your custom ARPs. Any Performances in any area can point to any other area (another Library, the same Library, the User area). You just have to be careful about moving around Libraries or deleting them later if you have another bank (user or another Library) referencing the Library you plan on deleting. It'd probably be best to keep some document that lists where you put everything and which Performance(s) use those ARPs.

Obviously, it would be best to keep everything together. The Performances that point to the ARPs you stick in a Library - also have them in the same Library. That way if you decide to delete the Library - there's nothing outside of that Library referencing those ARPs.

To handle the task more Jason mentions more easily you may need to get John Melas Waveform editor. Ive never used it but I think it can help to manage all that data. Do your research though

... note that if you keep everything associated - meaning all Performances that reference say Library "XYZ"'s custom ARPs are Performances only saved inside Library "XYZ" - then there is not a need to keep track. The rationale for keeping track is so you know, when you "mix up" locations for Performances vs. the locations of ARPs they reference, where everything is. It will let you understand if you delete a Library what happened and why perhaps some Performances in your user area referencing that Library now do not work properly.

This is why keeping everything together as discipline has been a suggestion of mine for a while. It allows for moving the Library around or deleting without fear of severing ties with other content that depends on the Library staying put.

The other way you can avoid having to keep track is if you can accomplish NEVER moving or deleting the Library. Then it doesn't matter what external Performances may or may not be referencing this Library because you have "etched in stone" the Library and vow never to move or delete it. However, you can see that this may place a constraint on yourself you later have second thoughts about. Later it may be more difficult to document the "ties" between banks.

And all of this can be avoided by just keeping the data associated together.

Since the built-in interface doesn't necessarily have all of the housekeeping extras to facilitate - you may find using software tools (as suggested previously by c) will make the task easier to manage.

Thanks a lot for your responses, I'm gonna dive into the library concept now!
I only have a bosendorfer piano library loaded so I should have still space.

Just to possibly add a few more ideas that may help, but would likely require a change in workflow from using Scenes ... have you considered combining all the drum tracks into a single Song, then set the Live Set to start the Performance via that Song, which would then play all the drum tracks in the same order without the use of Scenes..?
Another option is to modify the 'Audition' for the Performance you are using to play the Midi from the Song containing all the drum tracks, and then you just press the Audition button...