This feature is available in Catalyst, Enterprise, and Ultimate editions.
Inactivating a list value removes it from the drop-down list and prevents it from being used going forward. For existing items to which the option/value has already been assigned, the value still displays for historical and reporting purposes. This article provides instructions on how to inactive a drop-down menu option.
List Type Administration functions are only available to users with an Admin Privileges role of "System Administrator".
From the Admin menu, select List Types.
Select a List Type tab (Task, Test, Story/Backlog Item, etc.), and then navigate to the desired List Name section.
Click the arrow next to the Edit button, and then select Inactivate.