Steven Zahm@ Jeffrey
You can still do what you want, you just need to exclude the categories that should not be displayed or use the enable_category_by_root_parent if that will work for your category structure. I suggest the later method because it is the easiest and what most other users who need setup like your use.
Alternatively, you could use the option in the QuickTip. This method was developed specifically for another user who wanted to split categories but required that some be redirected to specific pages. Honestly, when the other user described what they wanted I didn’t really see why that would be useful… but, looking at it in action, it worked very well and accomplished his functionality goals.
See this page. Select Academia from the drop down. Upon selection, this actually redirected to a new page, look at the URL. On this page it was setup to display another set of specific categories. The site is still being worked on so there is not a whole lot of data to see it in action but it should show enough to see why this was wanted for their site.
I guess is what I trying to say… I develop for the 99% while still giving that 1% the options they need to create rather complex configurations.