Thread:The Many-Angled One/@comment-16461120-20170223045648/@comment-10473115-20170224190740

Edit buttons are little different than changing template. See Help:Custom edit buttons. But before editing MediaWiki:Common.js, consider which options are good default for everyone and which could be added just to personal edit button. See also: Help:JavaScript review process.

I can help if needed but it should be quite easy.