Extending a route

So I am in the process of planning a multiday motorcycle trip. The trip takes me through lots of little towns, some of which have lodging, some of which do not. As I start planning the route, I use the route planning tool (icon with connected boxes), clicking down waypoints to make sure the route goes on the roads I want to ride.

If I finish the route, and save the file, and later find out there is no lodging in the town, I cannot simply try to click on the last waypoint with the route creation tool and add waypoints extending the route to the next town. It actually seems to be creating a separate track.

It can't be this hard can it? I've watched every tutorial I can find and there is still no joy in Mudville.