Xiaomi
Set a Button Shortcut for Split Screen auf Xiaomi
On phones with on-screen navigation buttons, MIUI lets you assign split screen to a long press instead of digging through the recent apps overview. This saves time if you switch between two apps often, for example a chat app and a browser.
The shortcut is set through Settings ➔ Additional settings ➔ Button shortcuts ➔ Open Split screen. From there you pick which button should trigger the function: Long press the Home button, Long press the Menu button, or Long press the Back button.
Which button should you choose
The Menu button (Recent apps) is usually the safest pick, since a long press there rarely overlaps with another system gesture. Assigning it to Back or Home can feel faster, but it also means you lose the normal long-press action for that button while the shortcut is active.
This option only appears if your device still has physical or on-screen navigation buttons. Phones running full gesture navigation do not show this menu, since there is no button left to assign.