I'm trying to improve my use-case writing skills but I'm stuck on a certain scenario.

The idea is that there are a bunch of entries in a task list (some kind of todo list). Now the user wishes to process the list (divide it amongst other lists). He can do this by answering a series of questions / completing extra data. Based on the choices of the user the system perform different actions on the task.

I'm really confused on how to write this down in a use case.

What I was thinking is something like (I'm only writing down the main success scenario):

Use Case: Process Inbox
Primary Actor: User    

1. User indicates he/she wants to sort his/her inbox
2. System presents the next question and provides possible actions
3. User makes choice

_steps 2-3 get repeated until inbox is empty_

The problem with this is that it's not specific enough so something else I was thinking of is to make sub use-cases for all the different steps in the question process like:

Use Case: Handle Project
Level: Sub Use-case
Primary Actor: System    

1. System requests additional information (description, due date) from user.
2. User completes data
3. System classifies the task as a Project

What I'm puzzled about here is:

• How to include this sub use-case in my main scenario in a proper way
• How to indicate that after this action, the user starts again from step 2 in the main use case.

I was thinking of using extensions in which I include the different sub use-cases but it's getting pretty confusing.

So to bundle this request into one question:

Can someone clear up how you would usually tackle this kind of scenarios and/or provide me a basic possible solution for this example?

Thanks in advance ;)

If anyone is interested, the flowchart of questions I'm intending to use is from David Allen's book Getting Things Done: link to diagram