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When you try it in the GNOME Wayland session, a bump in the right down corner gracefully opens the tray, but you can't close it by bumping. In the standard X session however, when you bump the corner, it both opens and closes, producing weird behaviour. Just try leaving the mouse in the corner (so that it touches both edges and can't go further) and see what happens.
You can open the tray by bumping, but you must be darn quick.
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