I am following this doc to enable the Async save handler for Customer Service Hub, but I can not find the option of async save handler.

Did I missing anything? I can find this option in other apps, only Customer Service Hub get this issue.
I am following this doc to enable the Async save handler for Customer Service Hub, but I can not find the option of async save handler.

Did I missing anything? I can find this option in other apps, only Customer Service Hub get this issue.