Are you asking about using
a single .json skeleton with multiple.atlas files or
a single skeleton.json with multiple.png textures
Atlases support paging, e.g. you can have a single atlas backed by multiple texture.pngs.
If you want the Skeleton Loading system to search multiple atlases, then you will need to create your own AttachmentLoader class that retains a list of the atlases or a list of AtlasAttachmentLoaders.
Let me know if you can't get by with a single atlas with multiple backing pages and I'll show you the code to write your own attachment loader.
