Click on the map to add points. Double click to finalize path. Once a point been added, you can modify it by selecting it then dragging it to a new location. When a new point is entered, a temporary middle point appears. That point can be used to split portion of a path. So, new points can be added as needed.
Also, when pressing Shift key, you enter in delete mode. When in delete mode, clicking on a point of the path deletes the point. Releasing Shift key leaves delete mode.
Once a path has been finalized, you cannot it anymore.