The built-in "Joystick Button Recognition" option is intended for a single button (combination).
However, you can use commands to replicate that functionality.
E.G. if you want push-to-talk, you can create two commands:
One with the "When I press button" option selected, and its "Shortcut is invoked only when all buttons are released" option disabled (unchecked), containing the "Make VoiceAttack Start Listening" action
Another with the "When I press button" option selected, and its "Shortcut is invoked only when all buttons are released" option enabled (checked), containing the "Make VoiceAttack Stop Listening" action