In the Xiaomi smartphone settings, we can specify whether we want the App Toggle, Home, or Back buttons to appear, or whether we want to use gestures to control the device in full-screen mode. If the full-screen gestures are enabled, the following system navigation gestures apply

Android 10 (MIUI 12.0)
Step 1:  Open the  Settings
Step 2:  Tap on  Additional settings
Step 3:  Tap on  Full screen display
Step 4:  Choose  Buttons  or  Full screen gestures
  1. Open the Settings
  2. Tap on Additional settings
  3. Tap on Full screen display
  4. Choose Buttons or Full screen gestures

Xiaomi Instructions