Manual edge drawing mode can be enabled for each EdgeControl individually by setting the
ManualDrawing property to True. In this mode edge geometry path will not be generated or updated automatically leaving the user to deal with all of the mentioned stuff.
In manual mode there are severall methods that will become available:
EdgeControl.SetEdgePathManually(PathGeometry geo) - sets edge path geometry that will be drawn on the next render update.
EdgeControl.GetEdgePathManually() - gets current path geometry if any.
You can find an example in the Showcase app in Dynamic Graph tab.
Note that both of the mentioned methods will not work if ManualDrawing property is set to False.