Ben - I stayed away for a while, waiting for you to polish it, but I've given in to temptation and had another go this evening.
I suspect I've not properly educated myself on how to use it but........ Using the "Draw Track" option and set to "Walking" I input the 7 controls (plus start/finish) of my regular 201km ride. This delivers 200km exactly in Google Maps and rides as 201.5km on my Garmin. But on your GPXEditor I get 219km around a course which differs markedly from my usual route and which visually, is very obviously not the shortest path.
Am I misunderstanding this, or expecting it to do something it's not actually designed to do? Or just doing something wrong?
My guesses are, most likely first:
a) Where you actually clicked is a slightly different position from what google regards as the centre of the town when you create the route by inputting place names on 'get directions' on google maps
b) you had it on driving mode for some of the route, or there was possibly a bug that caused it to be actually on driving mode when it said it was on walking mode
c) there is some anomaly like a manual level crossing that google walking doesn't think you can get past when you can (more likely if combined with (a) )
(I am presuming the 219km is when you actually used gpxeditor t create it rather than just upload one created elsewhere)
so then:
Did you only click at the controls? And you had it on walking right from the start of when you created the track?
It's probably pretty easy for me to work out why it differed. I'll send you a pm so you can send me the file so I can take a look if you like.
You can re-route a segment if you like. Right click on any segment (you might have to choose 'stop drawing' first if you're in the middle of drawing a track) and choose 'reroute'. Move the mouse gently to where you want to reroute it through. When the line looks a better route, click the mouse (either button) and choose accept. If it goes haywire, click the mouse and choose 'cancel', and the track will go back to what it was like before you clicked reroute.
I'll get some guides up soon that will give you a step by step guide on how to use the features.
Thanks for persisting with it!