Accordian Menu Anti-Pattern
Accordian menus are currently very difficult to implment in Confluence...
Due to the dynamic nature of Confluence, it's best to try and avoid hard-coded menu strucutres. The more dynamic your navigation, the easier it is to add and manipulate content because you don't need to change the navigation - it adapts to your content.
Currently, the only reliable way to do any form of accordian menu, where sections of the menu expand and collapse and the current sections are highlighted, is to implement static HTML navigation with JavaScript to show and hide sections of the menu and also highlight the current section. This is a lot more pain than it's worth. Like many other anti-patterns here, it can be achieved, but we urge you to avoid it - at least for the time being.
Adaptavist are working on a solution to this problem. Well, we actually know how to solve it, but just haven't had time yet 