> an overlay in the web-based editor on desktop, and used that and satellite imagery as reference to draw in the missing trail.

If you added a gopro and SLAM to the GPS trace and imported USGS topographical data I wonder if you couldn't fully automate the process.

A decent representation of the actual path is usually pretty straightforward. The metadata and topology are more of the work.

In areas where 3dep is recent, you can usually see a trail under forest cover. It's pretty great.