We have a 2013 edge same engine and only fwd. it is in the manual. You turn the key counter-clockwise to stop. It will not allow a full turn off because the shifter latch is still unlocked since it is in neutral. It's by design no work-around.
The manual also states to start the vehicle every ~4 hours of towing. This is required more for the battery than anything, as all the electronics is not turned off.
Run a proper charge line from the coach to the edge. It will keep the battery from being drained by the electronics and the auxiliary braking system that should be installed.
14,000 miles plus towing ours with no issues. All we do when we stop for 30 minutes or more is put it in park, turn key to full off, remove key and lock it. Have gone as long as 2 days without starting it.
2007 Sightseer 35j
Bill: 2007 Sightseer 35J Ford V10