This is a problem with the new .cn6 script really. The currently released version doesn't only support 3 UV layers, it *requires* 3 UV layers which isn't very helpful. I've updated the script to create default values for UV layer 2 and 3 and attached it to this post. Will add to the scripts download in due course. Leaders and anything animated only need 1 UV layer. 2 or 3 UV layers are only used for inanimate objects like Buildings and Wonders. If you want to use multiple Materials/Textures in the same UV space you can simply assign different parts of your mesh to different Materials and the .cn6 export and import to CivNexus6 will create the separate Triangle Groups (as they are called within the Granny engine). If you import one of the Civ 6 leaders into Blender via the .cn6 format you can see how multiple Materials per mesh are used.