If an app's notifications are enabled on the OnePlus smartphone, we can choose to display incoming notifications as banners when the device is unlocked.

Banner notifications are displayed just above the status bar at the top of the screen.

Note: You can take immediate action by tapping the banner at any time until it disappears.

Android 10 | OxygenOS 10.0
Step 1:  Open the  Settings
Step 2:  Tap on  Apps & notifications
Step 3:  Tap on  See all apps
Step 4:  Choose an  app
Step 5:  Tap on  Notifications
Step 6:  Choose a  category
Step 7:  Enable or disable  Pop on screen
  1. Open the Settings
  2. Tap on Apps & notifications
  3. Tap on See all apps
  4. Choose an app
  5. Tap on Notifications
  6. Choose a category
  7. Enable or disable Pop on screen

OnePlus Instructions