I had the rear seat out on my 2012 Leaf several times - when water flooded the car, to install Wet Okole Seat Covers https://www.wetokole.com
and to deep clean later. Mine were easy to take out by lifting and pushing towards the rear of the car to make them come unclipped. My car has the heated rear seats and there is enough wire underneath for you to lift before detaching the wires afterwards. I would suggest looking at Youtube for videos.
2012 Nissan Leaf SL w 54900 miles SOH 60%. Lost four bars.