Basic understanding of how Notifications are treated in Plasma 6 version of KDE.
Also see basics of how system notifications are treated.
How do I write custom notifications? Starting with configuration locations on the filesystem.
How Knotifications are structured
Knotifications for Plasma 5 and 6 live in these default locations
Path type Linux and other UNIX operating systems
DesktopLocation "~/Desktop"
DocumentsLocation "~/Documents"
FontsLocation "~/.fonts", "~/.local/share/fonts", "/usr/local/share/fonts", "/usr/share/fonts"
ApplicationsLocation "~/.local/share/applications", "/usr/local/share/applications", "/usr/share/applications"
MusicLocation "~/Music"
MoviesLocation "~/Videos"
PicturesLocation "~/Pictures"
TempLocation "/tmp"
HomeLocation "~"
AppLocalDataLocation "~/.local/share/<APPNAME>", "/usr/local/share/<APPNAME>", "/usr/share/<APPNAME>"
CacheLocation "~/.cache/<APPNAME>"
StateLocation "~/.local/state/<APPNAME>"
GenericDataLocation "~/.local/share", "/usr/local/share", "/usr/share"
RuntimeLocation "/run/user/<USER>"
ConfigLocation "~/.config", "/etc/xdg"
GenericConfigLocation "~/.config", "/etc/xdg"
DownloadLocation "~/Downloads"
GenericCacheLocation "~/.cache"
GenericStateLocation "~/.local/state"
AppDataLocation "~/.local/share/<APPNAME>", "/usr/local/share/<APPNAME>", "/usr/share/<APPNAME>"
AppConfigLocation "~/.config/<APPNAME>", "/etc/xdg/<APPNAME>"
PublicShareLocation "~/Public"
TemplatesLocation "~/Templates"
The source of notifications is within
GenericDataLocation "~/.local/share", "/usr/local/share", "/usr/share"
I found the existing examples lived in /usr/share
Use the existing configs as examples you can copy & rewrite to taste within a different directory such as ~/.local.share to avoid any confusion. Chose this because it lives in the home directory and had no other configurations listed.