I recently acquired a front seat set of slightly used Coverking seat covers. No one seems to have made new covers for the 2018 Leaf, even though the Tech package adds a power driver's seat, and I was reluctant to pay $200+ for two seat covers that might not fit well. Tonight I installed them...
First, the Bad News: the power seat is not only not a great fit for the cover, but installation as designed is virtually impossible. Why? Because the Coverking covers (and I assume other brands as well) are designed with rear to front straps that fasten underneath the seats. There is not enough room beneath the Leaf power driver's seat to reach under and fasten strap buckles. There is barely enough room to fish the straps out under the seat backs, and the installation tool they provide is too short (as are the straps) to fish them to the very front of the seat. After wasting most of an hour trying, I finally used insulated wire to just connect the front and rear buckles. This is unsatisfactory both because it's crude, and because with no elastic in the straps, it doesn't properly tension the cover either. I will eventually replace the wire with elastic cord.
Now the good news: the passenger seat cover fits much better, although as with the driver's seat cover I ended up fastening the side straps to the lower rear straps, tucking them below the seat hinge covers. It looks better than the cheap universal covers I had on the seats, but you can still see that the covers aren't a perfect fit on the lower seat cushions.
This is just Odd: if you install the headrest covers so the gray stripe matches the stripes on the seats, they don't fit well at all - the areas that wrap the headrest support rods are in the wrong places. They only fit ok (not great) if you reverse them, putting the gray facing the back seats. I don't mind the black headrests, as my 2013 had them. Anyway, I'll add pictures one of these days...