Draw Over Other Apps Feature Not Available. One possible issue is the new persistent android system notifications on the galaxy s9. The display over other apps is an app specific requirement.
Once app is installed and is running with permission to display over other app, it shows notification when its swiped down. If an app requests this permission without you seeing a need for it, uninstall this app immediately. “draw over other apps” and “system settings.”
Long tap on that to get “minimise” option.
Under draw over other apps setting page. (in some phones, special access and draw over other apps) by now,you will be getting a list of apps,you can disable. Long tap on that to get “minimise” option. Click eraser, and then hold down the left mouse button and drag the eraser over what you want to erase.