Existing List Items allows you to Copy List Items from any list in your Content Group to another list. These items will act as if they are the same items even if they are in different lists. This means if you make a change to one list item it will affect the other item.
Go to the Jolt Web Portal select on Content > Lists. From here create a new list or go to an existing one.
1. Start adding items from by selecting +Existing Items.
2. You can select List Items from Active or Inactive Lists.
3. Select the arrow to transfer them to your new list.
4. Select Add when finished.