Version:            (using KDE 4.2.2)
Installed from:    Ubuntu Packages

Dragging an entry with the mouse shouldn't copy but move the entry. Shift+mouse might be suitable for copying, which IMHO isn't used very often in a menu editor. Default should be moving because it is IMHO more likely to sort entries than to duplicate them somewhere. Default KDE behaviour is: dragging a file/an entry and on dropping it the user is being asked what to do: move or copy. This behaviour also should be used in the menu editor. Please bear in mind that some people need one-hand moving (and copying) of entries/files so the standard KDE behaviour of asking on dropping is the most comfortable and sane behaviour you can provide.