Thanks oneandoneis2, ahh.
I have problems assigning "Word" and "Excel" buttons.
Their keycodes are 129 and 130, but KDE Menu Editor doesn't accept them.
E.g., "WWW" button is accepted by Menu Editor as XF86HomePage.
But there's no name for the above two buttons.
I added the following to ~/.Xmodmap :
Although Menu Editor doesn't accept the two buttons.
I have Genius comfy KB-16e scroll, but "xorgconf" had only KB-21e scroll.