Board Thread:Support Requests - Designing Your Wikia/@comment-26537866-20150823204115/@comment-25428589-20150823210226

On Terraria Wiki specifically, it's done with this JavaScript.

However, it would be a better idea to use the ExtendedNavigation tool at dev wiki, which is easier to use.

However (again), editing JavaScript is currently disabled Wikia-wide, so it is (currently) impossible to do if it's not already set up. Sorry.

I hope that helped answer your question :)