We can additionally protect apps on the OnePlus smartphone with a password request that immediately asks for the unlock method when the selected apps are opened.
The unlock method of the app lock is the lock screen password.
In addition, you can specify whether the content of notifications of locked apps should be displayed on the screen.

Note: If no screen lock has been set up yet, we will be forwarded directly to set it.

Android 10 | OxygenOS 10.0
Step 1:  Open the  Settings
Step 2:  Tap on  Utilities
Step 3:  Tap on  App locker
Step 4:  Tap on  Add apps
Step 5:  Choose the desired  apps
Step 6:  Tap on  Back
Step 7:  Enable or disable  Hide notification content
  1. Open the Settings
  2. Tap on Utilities
  3. Tap on App locker
  4. Tap on Add apps
  5. Choose the desired apps
  6. Tap on Back
  7. Enable or disable Hide notification content

OnePlus Instructions