Hello, hello. I'm JayRay, new to the community, just purshased AssetForge, and WAS a little dismayed by the inability to add custom textures, UNTIL I found a way to ensure my obj files and MTL files DID make the cut into the AssetForge with the Kenney Guide "Creating custom blocks"
However, I noted some times that my textures, no matter how I set them would be offset. This guide on wikipedia shows ALL the specs on how to offset those textures.