Sub-queues

I’ve been taking a look at RT, and am impressed - it’s pretty slick.
However, looking at some of the other ‘trackers’ out there, this seems to lack
a seemingly important functionality - that of having ‘sub-queues’ of requests
(of even sub-sub-queues…).
Am I missing something here?
Is the workflow idea behind this system different? If so, how?
If I have a large project, and want to create separate groups for that
project, e.g.
A_Project:

  • Documentation
  • Development
    • Core Modules
    • GUI
  • User-Support

… how would I go about setting up RT to handle this nicely?
Having them all at the same level would surely get rather messy…
Regards,
Cerion