Click the Custom Action tab. The Custom Action tab allows flow designers to add arbitrary activity properties which could later be used in the custom expiration handler or custom send action handler. Right-click on the Custom Properties window and select Add to add new property keys and values. For example, if the user wants to reassign a work item to another user when it expires, they can add a key of newUserLogin with a value of the login of another user besides the current actor for the activity. The keys or values added here become part of the work item and the work item will be sent to the reassigned user.
The keys or values added can also be a part of the custom send action handler or custom expiration handler. If this is the case, the code in the custom send action handler or custom expiration handler finds the user that they have entered in the properties and does a reassignment.
Note: The keys and values on the Properties tab can only be literal strings.