In the JIRA helpdesk want users to be able to categorize incidents by a drop down list of systems or areas, the incident is related to. Then later reports can be generated to show for which of our company's software products (or systems) we support that the various incidents are logged against.
So this probably comes back to being able to first create a custom drop down menu field and then being able to add that into the service desk portal as a mandatory item, as users are logging incidents.
Lastly being able to incorporate statistic's on the amount of various types of categories, into reports.
Michael.