As long as you have an adapter for the Leaf for a 30-20A or 50-20A you can use your normal 120V plug for the leaf, otherwise, you may need to build yourself an adapter that can go to 30A or 50A. Using the 20A adapter, it would be no different than plugging into a standard outlet. A 50A plug gets you the 240V the Leaf needs for faster charging.
Looking at the Owners Manual published by Nissan, it shows the acceptable towing methods to be 4 wheels OFF the ground (Trailer), or the REAR wheels on the ground (Dolly), and make sure you release the parking brake.