I’ve been considering my options for mapping in Urho3D for a while, my best options are either use an existing software, such as blender, and make maps in that. Maybe make a custom exporter to make the mapping pipeline a bit easier. The other option is to make a custom mapping solution from scratch based in and/or centered around Urho3D. Which one would you find more useful?
Poll: https://www.strawpoll.me/18518368
Blender, definitely. You have so much freedom. You could also use something like http://www.doombuilder.com/ or https://kristianduske.com/trenchbroom/ and then export an OBJ.
It really depends on the type of game and the associated maps that you are making. You may even want to create an editor that understands your game and your game only. If you’re working alone it might not even require a graphical interface, you’d just memorize keycuts.
Highways are useful because of their limitations. It’s what differentiates them from parking lots.
Because a game map is more then a collection of 3D models, it helps if your editor is built around Urho3D. As such it will be familiar with the available components - which could include your own - and using Urho’s render pipeline will make it WYSIWYG.