If you look at the manual at the 'Prefs BACKUP' command and think you will always create a config backup with the same items being included in the backup every time, create your own custom button that runs a command such as:
@nofilenamequoting
Prefs BACKUP=all TO "{s}Administrator - Opus Config ({date|MM-dd-YYYY} @ {time|hh;mm tt})"
2. If you think you might still want to use the UI to select what items to backup on an ad-hoc basis, then put your desired format string into the clipboard. It won't be automatic, but if you use a command like this you can then just hit <Ctrl+V> to paste the name you want into the dialog:
Steje's suggestions above both make sense (and this post doesn't replace either of them).
Adding to those, if you want to rename your existing backups to use your prefered format, a button like this will rename all selected backup files, using their existing names and Modified dates/times to generate the new names: