Thread:CAMERAwMUSTACHE/@comment-27700907-20160301032929/@comment-24264457-20160301132616

On the Classic editor you can scroll over to the side on source mode and the categories should be listed underneath the "Add Pictures and Media" section. If you scroll over a category there should be a trash can that you can click to delete the category. On the VisualEditor you can go into source mode and the categories will be listed on the bottom. Like      and so on.