I am not sure it is easily possible to have the sub-headings displayed dynamically.
It's possible. There's an extension for that. You can drill down right from the menu. It's dynamically built from the existing categories. The categories ARE the structural components of the wiki.
It does not have to be in the sidebar, it can be a separate page. Very necessary though, I would not have a wiki without it. It's easier to dynamically drill than navigate by opening several pages. It's also faster, and more comprehensive.
I am a gatherer. I much prefer to KEEP tags that we have, and add to them instead of removing existing tags and replace them with something else. The more links one has the better it is imho.
The problem with this is that the categories are the structure, so, we HAVE to recategorize as suggested http://forum.linuxmce.org/index.php/topic,11909.msg85208.html#msg85208
However, the categorization has to be exhaustive for each article. Each article must be tagged with all relevant categories.
Lets pretend that I insisted that the Homerun should go under TV, and you insisted that it appear under NAS We could put it in both places, just as current wiki articles can be set up to appear in "tutorials" and "hardware". But I suggest we avoid duplication if possible. ... If we have a 3-level structure, and if the index is always present at the left of the screen, then it is almost impossible to get lost.
There is a reason why shopping sites keep track of what you click on and make suggestions on what you should look at next, or what other people did following what you just did: thinking flows by association.
An article should be in as may categories at necessary.
If I just completed my install, it's just natural for me to wonder "what else" I should install before leaving the installation phase.