Embarrassed to say that I can't get the exported flight plan file to work in MSFS2020.  I reread the help file, studied the tutorial in it, and tried a number of things including changing the file extension, but I cannot see my flight plan file with MSFS2020. 

When I change the file extension I can see the flight plan file, but MSFS2020 doesn't seem to do anything with it when told to load it.  It's as-if I hadn't clicked on it.

Unfortunately there are plenty of issues when importing flight plans into MSFS:

To load a plan you have to export a MSFS PLN and load the PLN into MSFS. There is also another format offered to load in MSFS which is a situation file.

Alex