It is best to zoom in and auto-plot right up to the point where you want the detour to rejoin the route.
When creating a switchable diversion, choosing where the diversion is to start (on the current route) and the first new point on the diversion works fine with autoplot calculating a suitable cycle route following roads etc.. However, the next click to determine where the diversion should rejoin the original route results in just a straight line for the second part of the diversion . i.e. no autoplotting.
The diversion, with straight section, can be saved and then automatically 'reshaped' using anchor points etc. to correctly follow roads, but this obviously involves extra steps.
Any thoughts, suggestions?