Currently you can only mute the events of an app seperately, but there is no button that just mutes all notifications from that app, regardless of event channel. This would be especially useful for apps that don't have event channels implemented. Currently you can't mute their notifications at all.

Real world use case:

Apparently Spotify shows notifications on track change, that some people might want to see, but don't want their music interrupted by it. Spotify hasn't implemented event channels, and Plasma does not expose an option to mute all notifications for an app. (Relevant reddit post: https://www.reddit.com/r/kde/comments/106kpc3/nobara_best_way_to_mute_notifications_for_one/)

Some apps that have event channels implemented, have a lot of them. Users might want to mute/unmute all of them in one click. 

I personally would like to mute notifications from telegram, which also has not implemented event channels, but I'd still like to see them. I don't want to mute notifications for all apps, because other applications might have more important notifications I want to be alerted to with sound.

The solutions I see are

1. the obvious: adding a "mute this app" checkbox in the per app notification settings

2. this might be worth considering: adding an "all" event to every app, also to those without event channels. This has the benefit that other options like "log to a file" also become available.