Bad choice. That's the old file format. You cannot export the new bones with that format. New bones from Workspace doesn't transfer over to Modeler. And Modeler Bones are finally broken. Means there is absolutely no sense to use *.cob ...

As for the workflow, i already told a working art pipeline that is also good enough to export animation from Workspace. That one needs Ultimate Unwrap 3D though. But that's much cheaper than your solution here