ColorOS offers the split screen function on the Oppo smartphone, and spiltscreen is enabled by default on the device, but can also be disabled.

To start the splitscreen mode, wipe upwards with three fingers simultaneously.

Android 10 | ColorOS 7.0
Step 1:  Open the  Settings
Step 2:  Tap on  Split screen
Step 3:  Enable or Disable  Split screen
  1. Open the Settings
  2. Tap on Split screen
  3. Enable or Disable Split screen

Oppo Instructions