Need to be able to change startpoint in completed activity!

I just finished a BIG hike, but I neglected to start AllTrails until I completed a chunk of the route. I would love to be able to change the startpoint and get credit for having done the whole thing!  I also have occasionally had AllTrails stop recording in the middle of a hike and then start again; when that happens, I would like to be able to edit the entire activity, not just the endpoint.