-Edit your version of root.desktop (or create a new .desktop sidebar entry) to set "ShowHiddenFolders=true" and relaunch konqueror. Note the appearance of hidden folders in the sidebar for root, (but not other entries).
-Expand the sidebar tree and note that the horizontal scrollbar only appears when the contents do not fit, including the scrollbar not displaying when they do fit in the current area. Resize the sidebar to confirm.