Logging out of the graphical shell in a KDE Wayland session is not easy. Afaik on X11 that was easier. On Wayland the command: qdbus org.kde.ksmserver /KSMServer logout 0 0 1 works. If there is a better one, would be great to have available somewhere visible. Having that aliases to "logout" / having an executable in the Path to do that, would help usability.
Why isn't it easy? Just click on Kickoff > Log out. Adding such aliases is something better left to you.