If you continually forget to turn the car off, perhaps use the power button as the "Park" button. When the car is stationary and your footy is on the brake; just turn off the car. It will automatically put the car in Park.
That's what I've done all along. Problem avoided.
O/T but I got so used to this that when I rented an ICEV with pushbutton start, on the first day I repeatedly would turn off the car but not put the conventional transmission lever into Park first, which would leave the ignition energized.
It's one feature of the Leaf that I do miss now that I have an eGolf.
Oh and BTW that should read "foot on the brake" and not "footy on the brake." (I wrote that while using my smartphone so I didn't catch the error.)
Blue Ocean 2012 Leaf SV, lost that 1st bar at 34 months/26,435 miles. Lease returned 2 months later. Final LeafStat figures: 225 Gids, 17.44 kWH, SOC 91.89%, SOH 82.36%, 69.49% HX, 54.57 Ahr, battery temp 61.8 F.
Now driving a 2015 VW eGolf SEL.