How to export multiple UV's with glTF or GLB — Blender.Today
Can Cycles use multiple UV layers? - Blender Stack Exchange
Export UV Layout (Texture Maps for IMVU) – Blender Knowledgebase
Daily Blender Tip 269: Combine UV's from multiple objects - BlenderNation
I combined multiple textures maps into one in blender and joined the meshes after, but when I import it into Roblox the map is all over the place - Building Support -