By creating multiple rules with different scopes and actions, you can define a hierarchy of behaviour that Burp will apply to different applications and functions. For example, on a particular test you could define the following rules:

• For all requests, add cookies from Burp's cookie jar.

• For requests to a specific domain, validate that the current session with that application is still active, and if not, run a macro to log back in to the application, and update the cookie jar with the resulting session token.

• For requests to a specific URL containing the __csrftoken parameter, first run a macro to obtain a valid __csrftoken value, and use this when making the request.

This is phenomenally cool stuff that's getting added in 1.4...