With the new notification system in plasma 5.16, klipper notifications are shown in the category "Plasma Desktop Workspace". Klipper should instead have its own category. This would make it possible to configure notification settings for klipper individually.
Fix for 5.16: https://phabricator.kde.org/D21963 For master we might want to give it its own notifyrc to make it fully configurable: Bug 408989
Is resolved for a long time now