This is my scene hierarchy.
When you left-cick on the arrow next to Collection 1 you collapse the hierarchy beneath it, but when you shift left-cick on the arrow you open the full hierarchy beneath it, even though the arrow always works like a toggle, but not in this case. You can only shift left-cick on an fully opened hierarchy to collapse it. Quite unintuitive , isn’t it?
Please don’t say you would need to familiarise yourself with the new way this works, that is not an excuse for unintuitive design.
Shift left-cicking on an open object, the arrow next to it is pointing down, should completely collapse it, no matter whether the objects beneath it are open or not.