Just to be sure you know that : when you press escape, there you can load a flight plan. .pln are masked but as usual in windows, you can put a * in the filename input of the open file window and this will enable all files and there you can select a .pln file (generated from whatever source you want 
). It’s useful when you landed and want to go on for the next flight straight away without getting back to main menu.
I have never tested it but as it’s a flight plan, maybe you can load it while in flight? (I’d suggest putting the AP on basic HDG mode though).
Now I don’t know how ATC and the rest will react to this but somehow it’s like playing with the FMS or GPS in my opinion…