There are as many possible uses for User Defined Function Keys as there are keystrokes. Look at common commands you use on a day-to-day basis (similar to our <MENU> File Save Return Y example). Lotus users should consider making User Defined Function Keys for common keystrokes like @sum( or <MENU> Worksheet Column Set. MEMO users could create a User Defined Function Key with "Sincerely," followed by <ENTER> four times and your name. If you need to turn the sound on and off frequently you can create User Defined Function Keys to do so.
Most issues of The HP Palmtop Paper will contain examples. In the manual see page 21-14 for the discussion on creating User Defined Function Keys.