Don't know if your menu structure is the same, but in MEPIS 3.3.2 "K -> System -> Filesystem -> File Manager - Super User Mode" opens Konqueror as SU in file manager mode. -- I assume it's the file manager profile that you want, not the web browser. MEPIS even has a (half-size) icon for this in the Quick Launch area of the Panel.
I don't know if Kubuntu has the Quick Launcher enabled, but you can add it by r-clicking the Panel, then "Add -> Applet -> Quick Launcher". After that you can add whatever applications you want to it. The beauty of the Quick Launcher is that the icons in it are half height -- one quarter the area -- so they take up much less real estate on the Panel. Its presence is one of the reasons I instantly loved MEPIS, but realistically it's a KDE feature the anyone can use.