Thread:Love Robin/@comment-29688682-20161123142750/@comment-366087-20161123143855

Technically categories cannot be "merged" in the sense of taking 2 or more and clicking a button to make a new one. They cannot even be renamed like other pages can.

What has to happen is categories must be manually (or with a macro program; unsupported by Wikia) deleted from each page and new tags added and old categories then deleted when emptied. It is a long process unless you are an admin with one of a couple macro scripts.