Thanks for the input.
For sure there will be no absolute location on the globe. But it is possible to navigate relative to my home position. So I can in theory takeoff, move 5 meters forward, turn 90 degrees, move 5 meters again, etc. This is what I am trying to achieve and should be possible to achieve with a script or in a ground control station as well (in the thread I linked it is described for Mission Planner). Yet my tries with QGroundControl were unsuccessful so far.