I think it is fair to say that autopilot is not finished. It is easy to cause CTDs, can’t enter fixes as waypoints and a whole host of in-sim and SimConnect API issues.
Behaviour can change depending on where you create the flight plan such as external planner, main menu planner, in the GPS itself. And all fail one way or another frequently. Editing a plan either corrupts the plan or causes a CTD. Pretty annoying…