When two screens overlap during e.g. a presentation, automatically enable do not disturb mode.
As per usual with automatic do not disturb, it can be overruled by unchecking the checkbox in the notification plasmoid where it will be disabled until the screen configuration changes again and it still find a mirrored screen setup.

• Hit Meta+P, chose "mirror", dnd was engaged, popups hid
• Hit Meta+P again, chose "extend left", dnd was disabled
• Changed setting, it enabled/disabled live accordingly

Two questions:

• Should this be enabled by default? Are there instances where you want to mirror but have notifications? Mind that you can still "one time" overrule this if you need them for once, until you change screen config again
• Should the tooltip say anything, if so, what? We show "Do not disturb until $time" when a time is set but right now it doesn't say anything for mirrored screens. The applet icon changes to the crossed-out bell but the user has to click to find out what's going on.

There will be a followup patch to add a checkbox to notifications KCM