How to trigger a GCS to start using the normal transmitter/receiver

What are people’s thoughts on how to tell a companion computer GCS to take control?

An obvious thing would be to assign GUIDED mode to one of the transmitter switches. You would switch to GUIDED with the hand controller, the GCS would spot this in a heartbeat packet, and thereafter would take control.

I’d be grateful if someone more experienced than a beginner like me had something to suggest. Thanks in advance.