add waypoint to a route and save it

Hi,

I have been creating routes for my upcoming trip but sometimes I would miss out several waypoints when creating a route. When I tried adding new waypoints in-between waypoints already created in a route, the route would not go through the newly created waypoints. Is there anyway I can do that ? For example, I have a route created from point A to point B, I want to add point C in-between point A and B and create and save a route that would go from point A to point C then point B.

Thanks