When you use the savegame editor, each item has an item_kind_id. Unfortunately that editor doesn't have a very friendly interface - no way to search or even copy the data. So the only way to do anything ends up having to scroll one by one through thousands of them to find the item I'm looking for.
I don't know any other way to do this, so that's why I'm asking. The item_kinds.txt in the modules folder doesn't seem to have the item_kind_id.