Specify all the items that you want to add to the Checklist after the transition. You can select Append or Replace to append or replace the current Checklist current items respectively. To append only the items that do not exist in the list, select the Only append items that do not exist check box. By doing so, you can prevent items to be added again if the same transition is applied multiple times.
If you select Replace with no items in the list, the Checklist is reset to its initial state. Hence, an empty Checklist is created if there are no global items.
Global items are immutable
If you select Replace, the Checklist items which were added as global items via the custom field configuration page are not removed. These items are immutable. If you want to completely replace the Checklist, ensure that no global Checklist items have been specified in the configuration page.