Sets the identifier of an item that replaces the system-provided button in the Touch Bar.
To replace the system-provided button, set escapeKeyReplacementItemIdentifier to the identifier of an NSTouchBarItem instance. You must also include the item instance in the Touch Bar’s templateItems array, or return the item when the Touch Bar calls the touchBar:makeItemForIdentifier: delegate method.
Devices that include the Touch Bar (second generation) have a dedicated Escape key located to the left of the Touch Bar. By default, the Touch Bar hides the system-provided button and its replacement on these devices. However, if you set the replacement item's visibilityPriority to NSTouchBarItemPriorityHigh, the Touch Bar shows the item and reduces the visible space of the app region.