Board Thread:Support Requests - Designing Your Wikia/@comment-28776531-20151125154716/@comment-1647694-20151125160402

TheChromePerson wrote: ...I also can't find anything that enables me to edit like that rectangular box that says "Custom JavaScript status". Does anyone know how to enable that? ...

You can request Wikia staff to enable custom JS by contacting them at Special:Contact/general. See also Help:JavaScript review process.