It sounds like your use of "Category" is the Title of each Item... I am not fully grasping what you are requesting...
We did some research into Agenda when we started this project, but to be honest I don't believe we ever fully understood the part of Agenda you are referring to... If you can elaborate on the behaviour you desire, we will evaluate it and try to incorporate it if it makes sense in our application and is widely useful.
Perhaps some ascii art (or similar) of some fictious items (like your Projects example) would help clarify your feature request. Or you could attach a diagram to a forum post (or start an off-line email conversation @
support@kinook.com).