System Notification (Bell) to the leave_approver.

I want to send System Notification (Bell) to the leave_approver.
What need to mention in the condition for Recipient?

leave_approver==??

I have noticed that in the option Receiver By Document Field shows leave_approver if the notification type is Email.

In system notification there is no such option. It shows only owner. Don’t know why…

Yes correct… What is resolution for this?