Resume editing/creating orthogonal line?

To be honest, I have always had trouble with orthogonal lines. Now with OG 7.2 I still do. For right now, my problem is this. I’m creating a very long, complex line to represent routing of a heating cable in the floor. Inevitably, after some number of points are placed at the leading end, my clicking does something wrong and the line is apparently terminated. I can’t create any more endpoints. Then I am stuck with dragging the end to some later destination, and adding midpoints and dragging them to intermediate locations. It is considerably more tedious than clicking each point at the end.

So the question is, is there a way to get back in the creating mode, and place new points at the end?