Help adding items to non-vendor treasure tables?

[glibresult]

I'm trying to add items to things like chests or NPC inventories, but I haven't been able to get it to work.

For example, my TreasureTable.txt entry to add something to the Goblin Trader looks like this:

new treasuretable "GOB_Festivities_Trader"
CanMerge 1
new subtable "1,1"
object category "I_BookShield_Goblin",1,0,0,0,0,0,0,0

And the item "Bookshield_Goblin" shows up 100% of the time in his inventory.

I looked up the treasure table for the chest next to Alfira in the grove. But when I try adding

new treasuretable "DEN_BardChest"
CanMerge 1
new subtable "1,1"
object category "I_BookShield_Goblin",1,0,0,0,0,0,0,0

nothing happens. I tried looking at other mods, like seymordius' Rings Expanded but the only difference I can find between my code and theirs is the name of the object.

Can anyone help me? I really want to be able to add items into the world, and not just have them for sale.