As there are new groups policy, I'd propose either Graphical desktop/KDE, as it is quite pure KDE application, or System/Configuration/Other, as it is "a tool to manage the passwords on your KDE system. By using the KDE wallet subsystem it not only allows you to keep your own secrets but also to access and manage the passwords of every application that integrates with the KDE wallet". Maybe really "Security" group isn't right one