[rt-users] sub-queues

[Cerion Armour-Brown]

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