Xiaomi
Turn Quick Ball On or Off auf Xiaomi
Quick Ball is a floating shortcut button that MIUI places on the edge of the screen. It works independently from the on-screen or gesture navigation and stays visible over almost every app, including split-screen views.
By default it holds up to five shortcuts, such as going back, opening recent apps, locking the screen, or taking a screenshot. Some people disable it because it overlaps video players or games, others turn it on because they rarely use the bottom navigation bar.
Where the toggle sits
The switch lives in the same place across recent MIUI versions:
Settings ➔ Additional settings ➔ Quick ball
Inside that screen you get a single toggle to turn Quick Ball on or off. When it is on, you also get options to move its resting position along the screen edge and to pick which five shortcuts appear inside it.
If Quick Ball stays hidden after enabling it, check whether battery saver or a game mode is running, since both can temporarily suppress floating overlays.