What functionality is missing? What is unsatisfying with the current situation?

Currently a table of contents for categories, etc automatically shows up as un-expanded and you have to click each heading to see what's inside. This makes it difficult to see the entirely of content the TOC contains. It also is a little redundant with the world menu, since it also is essentially a content tree.  

How does this feature request address the current situation?

An option to choose to have the TOC expanded when the page is loaded would make it easier to see the entire contents of the TOC.  

What are other uses for this feature request?

It would make it easy to show groups of related articles easily. Having an automatically expandable option would make it easy to quickly aggregate related information.