Recently (finally) realized there was a way to collapse all branches in the sidebar folder tree. Unfortunately it’s alt + left-click, which on Windows does work, but when you release the alt key you also activate the program menu. In my case, who has that menu hidden, it also makes that menu appear (obviously).
This is rather annoying, because it means for me to collapse the branches I have to do alt + left-click (collapses tree and shows/activates menu), and then do alt again (which hides/deactivates the menu).
You should find a different key than alt for this, and regardless of what key it is, there should also be an option in the right-click menu and/or maybe a button in the sidebar header.