A nerdy way of doing things follows. If you have a gps file with a track you intend on following you can edit the file with a text editor to add waypoints for places of interest to you with names and descriptions of your choosing. I realize that not many will be comfortable doing this but I have done this often.
Files in the GPX and KML file formats are actually text files in formats similar to that used in HTM/HTML files though the text in GPX and KML are different. These files can be edited with text editors (though KMZ cannot). Some editors may require the filename suffix to be
.txt.
I recommend doing something similar to:
Copy example.gpx to my-example.txt
Rename example.gpx to original-example.gpx
Edit my-example.txt
When everything in works correctly
Rename my-example.txt to my-example.gpx
A link to a webpage showing how this can be done for a file in GPX format is