Yep, I have a separate Custom Prefab Editor window which is always open. BTW, I noticed the thumbnail generation is not working okay. It was okay until I added more custom connections and now randomly some of the thumbnails are not showing. I wonder how to could fix it - Image below. FYI: This is the latest ER but it used to happen in the previous versions too, Also note that when it loads/generates the thumbnails, it does load all the thumbnails but at the end, it will show blank thumbnails randomly as shown above. With that said, when I delete my custom prefabs from the "Custom Prefabs" folder of EasyRoads, everything goes back to normal!! EDIT: After I deleted my custom prefabs from the folder, I decided to restore the files one by one I noticed that the problem never showed up until I after restoring the 13th file, the problem reappeared. So if you have all the add-ons and demo files, if you add 13 more connections the problem starts to occur, apparently.