Hi Andy,
Currently the only way to configure the sidecar buttons is through the UC320W Configuration Utility. Another user editable speed dial short cut available is to program the speed dial via the phone LCD menu. Select the speed dial menu select the speed dial number, and the target. For example, if you wanted the digit 2 to speed dial 9 972 555 1212 you would, program that, then simply go offhook and dial 2#.
Hope this helps,
Chris