My method is to create a flightplan in LNM and export the .pln file to the flightplan folder then open it up on the flightplanner page in MSFS.
I would like to be able to export the entire flightplan, including SID, STAR and approach. The exported .pln file does not contain these. It only contains the departure airport, enroute waypoints and destination airport.
The .lnmpln file does contain these items thus my suggestion