For when you did not stop recording your ride at the cafe or your power meter has been playing up.

A self contained html page that allows you to view a gpx file route on a map, snip parts out of it, and save the changes back to gpx.

Also, a feature that allows you to select a section of the route, adjust the power values up or down by a percentage, and save the changes back to gpx. (It goes without saying that you should never use this to upload rides to Strava with inflated power data. It's only for correcting inaccurate data.)