I am struggling with imported components as well, and more specifically, imported 3D stp files. But I have something to offer in the way of importing components from vendors like Digikey and Mouser.
From Digikey, you might look for SnapEDA models. They have a selector panel for your schematic capture tool, and it includes both Eagle and Fusion 360 Electronics. I have found that .lbr file seem to work. However, .scr files, although they run, generate a few errors.
From Mouser, you might need to download a utility called Library Loader. That can accept Mouser ECAD files, which seem to be from Samacsys. They also work.
Octopart, of course, is the "native" component source.
If anyone wants more details, respond and I'll see what I can do.
If anyone knows how to insert a local .stp 3D model into a component in a library, give me a pointer or some idea of how to do it.
Thanks, /Bob/