As for macOS Notifications in System Preferences, can I restore the app which I deleted? I delete some apps in this window, and I cannot restore them even with the settings them apps.
Is there no way to restore these apps?
This looks that Not In Notification Center in this link is gone.
Remove an app from Notification Center preference pane



I think this is similar to the bug of the iOS in which if I select Don't Allow to send the notification when the app is installed, I couldn't modify the notification settings because the app did not exist in the list of notification settings.
https://discussions.apple.com/thread/7061805
This works for me!!
But I think that there is no Not In Notification Center is a bug, so I will post in the Apple's bug tracker system.

https://stackoverflow.com/a/51784565/7824640