Transition only properties
Introduction
Transition only card properties can only be modified via transitions, all team members are restricted from setting the value of the property without using a transition. This feature lets you lock down the allowable state changes on the property to only those where an explicit transition is provided. It also allows you to impose state based access restrictions, since particular transitions can be restricted to specific users. An obvious example is restricting the allowable states that a defect can be in before it is marked 'closed', you may require that only a defect in 'tested' state may be closed, and you might further want to restrict the ability to close defects to only specific team members. In this case you could mark the status property as transition only, then provide transitions to allow users to modify the status property appropriately - restricting the 'close defect' transition to only your tester
Project and Mingle admins can update transition only properties from the card view. Only team members are restricted to updating by transitions on all views.
Set property as transition only
To make a card property transition only, open the Customize card properties page by selecting Project admin tab > Card properties link.
Check the box in the Transition only column for the property you want to restrict. It is not possible to make formula properties transition only as they are already automatically derived.
Once you mark a card property as transition only, you will need to define transitions for each allowable modification scenario for that property, and make those transitions available to the appropriate team member(s)
You can uncheck the box in the Transition only column for a property to revert it to a generally accessible property.