Module -> extension ... the easiest way?

What’s the easiest way to take a large module and remove bits of it into individual extensions? Can I duplicate the module, make any duplicated file(s) a .mdx, and then edit that mdx to strip out the stuff that is (i.e., what will become) the main module?

For example: I have a module that contains four battles set-ups in it. I want to leave the main module to contain only battle A, and create separate extensions for battles B, C and D.


Figured it out.