Tom,
I have recently also needed some track editing capabilities, as I seem to occasionally start a loaded mountainbiking training on accident as I get back in my car to leave the trails. A few miles down the road I notice that it's recording and I stop it.
What if there were an option during portal upload to break laps or active sections apart into separate uploads? That way, I could just delete the accidental portion of the training.
Editing the track is not possible - as you stated correctly. But you can convert the training to a 'navigation route' and edit the route in Route Planner.
It would be nice if you can edit the track as well when your editing the train profile, The things you can change now is Training title, Sport, Desciption and Link. Since I had a bad reception on my GPS and I've edited the route afterwards, it would be great to choose the actual track (route) that was made.