Maintaining a choice of Nav GPS systems (750 or 530/430)- exit the SIM or aircraft by going backwards to Main Window, then quit to Desktop. Do not Quit via Steam !
Workaround for loading flight plans into G530/430 reliably-
Create .PLN file in Little Nav Map (or Simbrief)
Export flight plan as .PLN to a folder of choice (choose that plan in MSFS with Load/save option
Set time of departure at location (neither Live Weather or Time slider are available after starting the flight)
Save flight plan using the Load/Save option in the Map screen to SAVE the plan as a .FLT file in same folder (or other folder)
Load that .FLT file back into the Map using the Load/Save option (plan should now appear in running G530/430)
Set up the aircraft for Flight.
To change the plan or aircraft, follow this scheme back to Main menu page and select a new plan or new aircraft. I only tried this 4 times, rebooting once because of locked SIM, and it worked reliably. Prior to this I was lucky to get any plan to load from the Load/Save button into the Blacksquare TBM850. I have yet to try Bonanza or Baron.