It will let you change things when you are not moving - even when it's
in drive. You can zoom in and out, add waypoints and destinations by
scrolling through the map and zooming in and out, but you can't add by
address/phone/saved points - which is strange. That's the easiest way
to change your route - so those should be easier to do while driving
Even if they enabled it when it detects someone in the passenger seat -
that would be fine, too!