It would be helpful if it was simpler to give a route a meaningful name.
Of course you can give the file any name you like, but a Garmin does not take much notice of that; it uses the name specified in the xml to list the available routes / tracks / etc.. It seems that the cycle.travel gpx creator always sets that to "cycle.travel" for .tcx files and "ACTIVE LOG" for gpx tracks. So a manual step is necessary to set the name to something specific.
Possibly this may be why some users say they can't find the routes they have downloaded.