Click on streets in the order you'd like to go. Then the router connects the street where you are to the first street you clicked on, then it connects the first to the 2nd, 2nd to the 3rd,... instead of just clicking on the last street like we do now. It might be simpler to program than drag and drop.
this would be nice. it would help you knock off some of your unvisited streets on your way to your destination instead of taking the same route every time.