Board Thread:Support Requests - Getting Technical/@comment-33359237-20180608115016/@comment-1038387-20180608120619

Do you mean the WikiNavigation? See this help page. You have to link to a page or category; in essence, it's already a small customizable category tree, with three levels

The link is not recognized as a wiki page because... it's not a wiki page. You can't use it there, and you shouldn't; the category tree is larger than the limits of the WikiNavigation.