Documentation writing is a "chore" There are people willing to do it, but they dont last long because the development of Tiki is fast moving.
Developers wont document, and really people do what are interested in doing. If you can bring any quality of documentation big or small to Tiki its more than welcome.
doc.tikiwiki.org is meant to be the place where it all happens, however sometimes more documentation exists for a feature here on tw.o somewhere in the mess of the wiki pages, forums or FAQs.
Hotwords in new windows, basically does what it says. It open the hotword in a new window. HotWord documetnation does exist here on tw.o
Featured Links are basically a menu, click the Admin->links and you can set them up.
MniCalendar is a pointless feature imho
Dynamic Content has documentation here on tw.o
EditTemplates doesnt work in 1.8.3> successfully anyway, fix is pending. but it allows you to customise the layout and style of your tiki through the web browser
Smarty just read the http://smarty.php.net user manual I dont see any point why Tiki should rewrite that excellent documentation.
PHPLayers docs only exists in the code itself. myself and mose are the guilty ones there.