title: How do you define a main page hierarchy in Doxygen?
body: <p>On this Doxygen generated help page <a href="http://api.fluffyunderware.com/curvy/index.html" rel="nofollow noreferrer">http://api.fluffyunderware.com/curvy/index.html</a>, there is a hierarchical documentation index for the main page and a table of contents.  How do I replicate this capability in my own documentation?</p>
  
  <p>Here is a screenshot of the mentioned page:</p>
  
  <p><a href="https://i.stack.imgur.com/MVtvW.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/MVtvW.jpg" alt="enter image description here"></a></p>