Hi! I don't see any reference to preprocessing API object in the docs:
https://www.zabbix.com/documentation/3.4/manual/api/reference/item/create
is there any?

For example there is a link that describes item object:
https://www.zabbix.com/documentation/3.4/manual/api/reference/item/object
but not preprocessing object that is mentrioned in the item.