[enricofra]

Ok, I've in some way fixed this. I've changed every task in a project, then collected thm under a single folder. Maybe I was misunderstanding the OF model: subtasks are just a visual way to organize to-dos, but the real brick here is the single project. And projects can be collected with folders and context, on which I can focus and so avoid the mess of too many tasks in the same window.
so:
- Main list
- > Folder
- >> Project
- >>> Tasks

and not:
- Main list
- > Project
- >> Tasks
- >>> SubTasks

So, I have some last words on this kind of problems...
DEAR FOLKS AT OG, I REALLY THINK IT'S TIME TO HAVE A GOOD EXPERT TUTORIAL FOR OF!!!
Video, PDF or interative Flash is your choice. I cannot loose so much time to find the best way to use OF.
This problem doesn't exist in more simple tools, like Things and others, but with OF a tutorial can really make the difference between an happy and a leaving customer.

Bye
Enrico