Here are the result of my flight log and registered flight plan.
During this flight, planned mission is executed twice. There is a short stabilize part to check the bird, with Arm, Flight, Disarm.
Next I proceed to Auto Flight. For it, I didn’t arm the motors, I just slide the Start Mission “button” on the GCS Screen. You can have the same result when manually arming the motors and switch “Auto mode”. Spline waypoints part of the flight is with variable height (descend then climb) while looking the ROI.
After reaching point 12, it RTL, land at Arming-TakeOff point and disarm. I repeat the process for second flight…
Here is the Planning screen
In the Mission End line, Return to launch is checked (not on the picture).
No need to add a RTL order after waypoint 12 or to specify a landing height (ref your question)
I have a question: with QGroundControl, Flight plan is saved to the Edge (Upload button). When connecting for next flight, flight plan data is downloaded to the computer, but I see no option to save a flight plan to computer for archive or mission preparation. It is possible to do it with Mission Planner.