However, you can certainly accomplish what you're asking about with existing tags. I would create a special piece called "shuffler", that is the same type as your other cards.
After moving your nine cards into the deck, also move the shuffler piece by name. Then run apply a shuffle_location action, using the "shuffle_location" action, applied to the "shuffler" piece (see the xml line below). For some reason, the ability to supply a target piece was left of of the docs, but it works for shuffle_location, just like every other action.
Now that the 9 card deck is shuffled, you can move the "shuffler" piece out again by name, and store it off-screen in some hidden location, ready for the next time somebody hits a button.
<quad_tap -- 9 moves>
...
<quad_tap -- move shuffler>
<quad_tap action="shuffle_location" args="shuffler">
<quad_tap -- move shuffler back to hidden location>
<piece>Button</piece>
-Nathaniel
Sent from my iPad