It seems that there is no way to easily link to other wiki pages using the new Markdown syntax, which is apparently now the default, even on new pages created within Creole-only wikis. Additionally, the documentation makes no reference to wiki-linking at all.
Ideally, it should work similarly to other Markdown-based wiki systems, such as the one used on Sourceforge.
I attempted to try different methods, but none of them worked, outside of creating full URLs.
Wiki-linking is a very curious omission considering this is a Wiki system.