I've never even played the game, but if there are no triggers than it is done in the data editor. It is possible to do things with ammo.
Example being an apple is ammo 1. A knife is ammo 2. When Ammo 1 and 2 are held in the inventory together or a specific ability is used, it creates ammo 3 which is diced apples. Though using triggers would be much simpler.