Re: create a route from waypoint list
When you create a route interactively, if at any time you click on the location of an existing waypoint, the system will ask you if you want to use the already defined point or use a separate one. That's the only way you can do it right now.
I've given the editing of routes from the Route Properties window a bit of thought, but the only thing that seemed reasonable to do was removing points from a route. I was stopped both by the unclear question of how to do the UI around adding existing points to a route, and the amount of coding needed to implement it.