Please check the Betaflight github documentation about GPS rescue before using it to fully understand it's functionality:
https://github.com/betaflight/betaflight/wiki/GPS-rescue-mode
Joshua Bardwell also released a video with loads of information about this feature:
https://www.youtube.com/watch?v=B_Yl0wqRf68
Below our flyers that come with every GPS pre-installed BNF to make your FPV journey as easy and safe as possible!
Rescue Operation:
① If GPS rescue mode is triggered automatically, take control by moving either stick, not by toggling the GPS
rescue switch.
② If manually triggered, toggle the rescue switch again to regain control after the aircraft returns.
If the GPS rescue mode is automatically triggered and the remote controller successfully takes over, manually
toggling the switch will reactivate GPS rescue mode. If the rescue conditions are not met, this will cause the drone
to disarm and fall.