Ahhh depending on if it was imported as a Skeletal Mesh it could be the SKM tree, you can access it by finding the Skeletal Mesh file for the mesh you imported and opening it up. However this primarily shows off bones, if you have just groups it may “create” bones, but matches your description!
If not, you may have been working in a blueprint (Like a prefab in Unity) but unless each piece was a separate SM you wouldn’t have a hierarchy, so it’s likely the first answer but I thought I’d give possible visuals to try and jog your memory if I was wrong!
