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There are a couple of different ways to control the abandonment point. At any time during the flight you can push the return to home button on the remote or the Home button on the app to trigger an abandonment point to be dropped and tell the aircraft to return to the takeoff point.
It is also possible to set the battery timer in the settings to automatically return after a fixed amount of time.
Switching from F to P is basically telling the aircraft to stop listening to 3rd party apps. It is there as a safety.
Any of these three methods can be used to create the abandonment point. We are somewhat limited to what we can do by the DJI SDK.