I figured this out.  I clicked on the map to add a "route point".  Then in the screen that has the caluclation results, route points, and a whole bunch of other settings, I moved the new route point up to the location I wanted it in the trip.  After that, I clicked on "Find Route" so the route would recalculate.  The I clicked Save Map in the calculation results screen.

Not the most intuitive, but it works.