Thread:SonOfAres1/@comment-1519475-20161230014226/@comment-26917787-20161230014556

If you open the Source Editor, there is a menu on the right hand side with various options. If you scroll down, there is an "Add Category" option, with a list of the pre-existing categories of the article. There's a trash can icon next to any category you hover over which will remove the category from the article.