Also to note, Even though Spell IDs don't work, Item IDs do. There are also other ways to use items. You can refer to the inventory slot they're equipped in for equipped items and you can also refer to Bag & Slot IDs.
#Use Hearthstone by ItemID 6948
#Activate Trinket 1 by InventoryID 13
#Activate item in Bag 0, Slot 1
#Bag IDs range 0-4 increasing right-to-left (Bag 0 is Backpack)
#Slot IDs start at index 1, increasing left-to-right, then top-to-bottom (Slot 1 is upper left slot)
/use 0 1