I don’t have an “Add” button next to Screen recording

Take a screen recording on iPhone

1. Go to Settings > Control Center, then tap. next to Screen Recording.
2. Open Control Center, tap. , then wait for the 3-second countdown.
3. To stop recording, open Control Center, tap. or the red status bar at the top of the screen, then tap Stop.

Take a screen recording on iPhone - Apple Support (IN)

See the pic below which is self-explanatory