Not sure what the issue is with tail lights on 2018 Ford Edge to make it towable. We have a 2018 Ford Edge. We tow it behind our 2008 Beaver. I got a light kit from Roadmaster and did it myself in about two hours. Was not a problem. You need the Edge with the 3.5 V6. You can not flat tow the 2.0 Ecoboost (which is the majority of those on the lot). We had a 2014 Edge before this one and towed it for 20k miles. PM me if you need the light kit part number. It is on the Roadmaster web site with a video of how to wire it.
Mark and Evelyn
2008 Beaver Marquis Amethyst 45ft, 600 CAT
2018 Ford Edge (toad)...Alaska Residents