I used to be able to push the top of Firefox browser window above the top of the screen. This is no longer possible - the window keeps snapping back inside the top of the screen. (Sides do not have this behavior - I can push a window sideways off the screen.)
When top of the window is at the top of the screen there is a small gap of inert space above the tabs. Moving my cursor to the top of the screen to switch tabs with top snapping inside screen now means I have to add a Y-axis mousing as well. When I was able to push the top of the window just a bit above the top of the screen I only had to push my cursor to the top of the screen, and then I only had to mouse X-axis to select any tab.
I'm not good mousing so having the only X-axis mousing to pick tabs was much easier.
I want that back.