For example, if we use Bluetooth headsets or speakers, we need to connect the devices together, and for this to happen, Bluetooth must be turned on.

Note: We can also turn Bluetooth on and off on the Xiaomi smartphone using the Quick Launch bar, but we recommend turning it off when not in use to conserve battery power.

Android 10 (MIUI 12.0)
Step 1:  Open the  Settings
Step 2:  Tap on  Bluetooth
Step 3:  Enable or disable  Bluetooth
  1. Open the Settings
  2. Tap on Bluetooth
  3. Enable or disable Bluetooth

Xiaomi Instructions