I have used Toodledo for a year. I don't use the subtasks anymore - subs kept getting lost or hidden, and my system was repelling me. I have folders for Projects, Next Actions, Waiting For, and Someday/Maybe, and I just move the tasks from folder to folder during my weekly review as needs change.

The tasks in the Projects folder are written as desired outcomes with project support in the notes field. When I view this folder, the tasks show as a flat index of my projects. Tasks in my Next Actions folder are assigned contexts, so I can print a list of the Next Actions folder by context, or easily review a particular context on my iPhone. Waiting for and Someday/Maybe folders are for tasks I'm incubating or have delegated. To specifically answer your question about projects you've put on hold, I would just move them from my Projects folder to my Someday/Maybe folder. If you do this often, you could have a Projects-On-Hold folder similar to a S/M folder, in that you'd only review it once a week or so rather than daily, as you'd review your active list of projects.

I don't use the status fields at all. I have found that the more variable to enter, the less I want to use the system, so I keep it very, very simple. Hope that helps!