I just finished riding the GAP trail from Pittsburgh to Cumberland. There really isn't much chance of getting lost so I got to experiment a little with the Rox and my Komoot route.
Like I said, on day 1 I stopped when I felt I covered enough ground--Ohiopyle--stopped recording, and the Rox saved that segment.
On day 2 when I started in Ohiopyle, I just selected the same route (starting in Pittsburgh) and the Rox asked me if I wanted to navigate to the start or start from where I was and navigate to the closest point on the route. When I chose the latter, it's like I continued where I left off.
When I got to Cumberland at the end of the day and stopped recording, it saved that segment.
So I guess it's doing pretty much what I wanted it to do which was a nice surprise.
Paul