Organize Package

[qwerty]

Actually you express this via nesting elements.
- Use Case
-- Context diagram
-- Scenario (found in the properties)
-- Activity element (per scenario)
--- Activity diagram
--- Actions of this activity

I recommend to describe a use case either with scenarios (according to Cockburn) in a textual manner or to use diagrams (above Activity elements with sub-structure) and not to mix both in a single use case. Textual is preferred where you have a rather linear number of steps without many exceptions/involved actors.

I'm currently writing a book where this process is described in more detail.

q.