@duerer unfortunately Collections are never sorted alphabetically, but in the order they are created/Appended…
Remember that Collections are numbered; if you press 3, for instance, it shows the third Collection and hides all the others.
When alphabetizing Collections, they should also be re-numbered.
I don’t think this two-line fix:
https://developer.blender.org/rBSaff8ce438a1f856f44e92319063950d7fc500c24
takes that into account, but still, it is a known bug and someone is working on it.
