If the Edge Lighting is used on the Samsung device, only the messages app is displayed by default. In the sidelight settings, you can add more apps if they are supported. Alternatively, you can activate an option that automatically activates all apps for the Edge Lighting notifications.

Android 10 | One UI 2.0
Step 1:  Open the  Settings
Step 2:  Tap on  Display
Step 3:  Tap on  Edge screen
Step 4:  Tap on  Edge lighting
Step 5:  Tap on  Choose apps
Step 6:  Enable or disable desired  apps
  1. Open the Settings
  2. Tap on Display
  3. Tap on Edge screen
  4. Tap on Edge lighting
  5. Tap on Choose apps
  6. Enable or disable desired apps

Samsung Instructions