Re: Is it possible to duplicate whole categories of pages?
I take it you already have created the objects in your first category, but not the objects in the new categories. I don't think there's any way to do what you are describing using the Tiki admin tools. But if you have some familiarity with using phpMyAdmin to access the database tables directly, I can describe a kind of "back-door" way to add or modify Tiki content. (phpMyAdmin is an essential tool any time you're using PHP and MySQL on a web site, IMO.)
I'm not really an sql whiz by any stretch, but I've used phpMyAdmin to speed up repetitive Tiki tasks. For example I wanted to make a new menu that was very similar to an existing menu (with quite a few links). Rather than make the menu with Tiki (adding one link at a time), I just downloaded and copied the relevant database table, studied what needed to be duplicated and modified (in a text editor), and uploaded the new, appended table content. Of course in the case of this menu, the pages referred to already existed. If I added link a pointing to a yet-to-be-created page, naturally I'd get a page not found error trying to use it. The same would be true for a category created and populated with "links" but no objects at the end of them.
You could do something similar with the category-related tables. But really the hard part of making and populating the new categories isn't doing the categories themselves, but making the objects to be categorized. This being the case, you might want to try the copy-and-modify approach with the tables containing wiki pages, quizzes, articles, etc. themselves. Then do the categorization in the regular Tiki way. Let me know if this sounds any better than doing it the regular way, and I can maybe give more specific details.
-- Gary