Add an option with "Don't ask again" in the corresponding close dialog when an user want to close the application (clicked the quit/exit button in the system try context menu).
Confirmed as a valid wish, which would have been a better way to eliminate any potential annoyance. However, the question when quitting an application from the system tray has now been removed completely by https://invent.kde.org/frameworks/kstatusnotifieritem/-/commit/f8fecc15 and so there is no dialogue to set "don't ask again".