User defined RTL path or MRTL

Can we use any present parametrs of ardupilot for misson RTL or user defined RTL path where we can add seperate waypoints as RTL approch apart from misson WAYPOINTS is any way to impelement this without any firmware code changes , also is it possible to upload two different missons to flight controller ?

Check out this thread:

objective is need to upload the RTL path with as seperate from misson path and upload both misson and RTL path

I did it with a script. But obviously thats not what you are looking for. As far as I know, no except there is a work around. Like goto waypoint. For example first set of mission is your plane a that ends with a land or something that would null the mission in an error. The drone will just stop and not continue on to second set. At the back. You can manually trigger a goto where it jump to the back waypoints. Only issue is you have to manually trigger it.

This is of course a bug and loophole if its what you are looking for. Writing a proper script makes more sense and better.