I am a new tiki user/admin, so bear with me if I am missing some simple configuration. I did my best to read the documents and will be using them to show my struggle.
I was able to create a new menu module using a structure. However this is not displaying the full 'toc' of the structure, and instead just the main page, so the 'menu' isn't much of a menu! Here are some screen shots of my config and resulting look and feel.
I blacked out the wiki/structure name, as it is identifiable. It shouldn't be important, but let me know if 'you' thinks it is.
This page seems to indicate what I want is possible, though it might be outdated. https://doc.tiki.org/Structure-Admin
Create a Menu from a structure toc
You can create Menus from structure table of contents by means of several ways: