Drag your routes, not your feet!
Think you can do better than Furkot at choosing your route? Or may be you need to visit a place that seems out of way. Grab the blue route on the map and drop it in another place. The route is repainted while you're dragging it. Furkot will add a stop in the place where you dropped the route.
If you don't like the end result you can just delete the added stop.
You can also drag your stops: move them around and watch Furkot repaint routes and recalculate distances and times.