I don’t know where to report the bug, but I’ll write it here:
I wanted to create my own UV for lightmap, so I just duplicated UV tag in Cinema 4D and named them 1 and 2. When I import to UE, it’s imported second UV map okay (don’t forget to uncheck Generate UV light map). So technically it works and catching my second UV as lightmap. This object currently has one material, when I adding second material (Selection Tag and applying material to the selection) it has 2 materials and 2 uv. Technically everything is correct.
Bug: When I import this FBX to UE, I have two “options”: Either have only one material and 2 UV (one is my own UV and second is my own as well for light map, technically it’s the same UV layout) OR I can have 2 materials (or full materials set in case if there many) but it cannot see second UV map, I have to go to the object properties and Generate second UV for lightmap, when I click Apply, magically it generates lightmap UV (removes my own UV map for lightmap or overwriting it) and showing me all materials as it was on the object, this way I loossing second UV.
it’s very odd glitch, I cannot track who have a bug Cinema 4D or Unreal Engine. Currently, I use generating UV for objects with many materials and using second UV only for object with one material. Can you please have a look to this? it’s kind of annoying, if it’s UE4 bug, I would is as high impoirtance.