Board Thread:Support Requests - Designing Your Wikia/@comment-2003555-20151026225547/@comment-26334172-20151027215243

Assuming JS isn't locked up, you simply copy the codes from those pages into MediaWiki:Wikia.js. Or, to keep things cleaner, make pages "MediaWiki:UserTags.js" and "MediaWiki:MarkForDeletion.js" and use importScriptPage="..." on Wikia.js.

At least I think that's how it works. :P