I'm in the process of working on the DIY for horn upgrades for the 2018 LEAF.
It is a bit more difficult this year, as the front radiator is completely surrounded by ductwork to funnel outside air through the engine compartment and back over the traction battery now. Getting to this area to work will require the entire front bumper cover to be removed.
The horn is in the lower righthand side of the front bumper cover, and it is quite tight in there, so I am working on a rig that will put the horn in the motor compartment and run a power/ground line back to where the original horn is at. To get at this to connect the wires, It will best be done by removing the right front wheel and the wheel well liner.
I have other things in the queue to finish first, but the wiring will be the same as the older car, with just the packaging being new.
2018 LEAF SL
Delivery April 10 2018
2014 LEAF SV
Delivery May 23 2014
50,000+ miles - all 12 bars - Same range as new - No warranty issues ever!