This is a feature request of sorts… I know that one can load a flightplan into MSFS 2020 and fly it with all of the fixes and navigational gps points, if you load the flightplan before the flight begins, but I think it would be neat if MSFS 2020 gave the option to store and save, and even enter a flightplan from Simbrief into the sim after the official start of the sim session.
Part of the reason I’d like this feature is because I fly on Vatsim occasionally (which MSFS 2020 does a fantastic job doing btw), but after I had already filed my flightplan, clearance delivery modified my flightplan that was already loaded into the sim “as is.” It was a struggle to get the new fixes inserted “into the box” … it was doable, but I think this feature could be improved?