Sets a list of identifiers for items to show in the Touch Bar’s customization UI.
The customization UI shows these items in additional to the items in DefaultItemIdentifiers.
The items you include in CustomizationAllowedItemIdentifiers appear individually in the customization UI, arranged in the same order as you specify in the array. As long as there’s available geometric space, a user can drag in to the associated bar any of the items in this list.
Always configure this property for a customizable bar.