How do I add a new import format for skeletal meshes?

I want to manually load data from various source files (there is only one root file describing the mesh though). Some files have morphs that need to be baked into the original mesh. Some morphs can’t be exported through regular means which is another reason I want to add a custom importer. I have the vertices, uvs, weight maps, bones, surface groupings, etc. It looks like FSkeletalMeshImportData is a close match to the info I have.

My question is this. How do I add a new skeletal mesh import format? I can’t seem to find any docs on this. Looking at the code, I keep running into a Reimport factory class. But I don’t want to reimport. Basically, the two critical points I’m missing are how to add the new format to the import dialog and have this hook into my code. The second point is how to convert something like FSkeletalMeshImportData into a USkeletalMesh (or rather a USkeletalMeshComponent) that is saved as an asset. I was able to add a TIFF import. But that one was simple. I don’t see anything simple about any kind of interface for mesh import. If someone could point me in the right direction, it would be much appreciated. Thanks!

edit: The above would be done in the editor only.

While I’m at it, I want to ask if it’s possible to change the rotation order of a joint/bone? I need to change them individually. So a bone could have YZX instead of ZYX for example.