Join a route half way round.

If I download a route from, say, Kamoot, and I want to join the route at an intermediate point not at the start how do I do it?

All I can see is no option but to ride to the start of the route. Even then Explore 2 Buggered me up. I then had to start the navigation again at the start! Surely the device should continue me onto the route and take me round once I get to the beginning point.

Not ideal at all!