A post was made last year about how newer versions of Unreal engine 5.5-5.7 removed the toggle that combines skeletal meshes during import. https://forums.unrealengine.com/t/gltf-combine-skeletal-meshes-import-option-gone/2141269
I went on 5.7 yesterday to find that this option is still not restored, even though the developer in the previous post opened a ticket for it. I was wondering when this toggle will return, and I would assume this is not something that would require a whole lot of work either? I have not looked at the source code, but it sounded like the property is still in the code just that it is not exposed to the UI?