During Vargas camp Trey uses magic to deflect a large stone that is thrown at him by the Vargas Monster, casts a barrier spell and uses magic to freeze grass.
Trey uses magic to muffle sound and an unspecified attack magic during Playfulland to break things apart.
Trey also uses an unspecified form of attack magic in Book 7 against darkness summoned by Malleus and against Malleus himself.
When asked what is it he likes about being able to use magic he says he uses it to keep eggs from dropping to the floor.
Trey uses clothes-changing magic in Book 7, and wind magic during the Nightmare Before Christmas event to keep Sally from hitting the ground after she jumps out a window.
It is possible that Trey also uses wind magic in Book 7 in order to cushion his landing after a fall.
Twisted Wonderland Reference Note 