Actions: ADD_ITEMS, REMOVE_ITEMS, and REPLACE_ITEMS operate at the PRODUCT (item) level, not at the SKU level. ADD_ITEMS will add new products to the collection or update existing if they already exist. Notes: 1. Sending SKUs is optional, not sending SKUs will add all SKUs of that product to the collection. 2. Sending a list of SKUs will replace existing SKUs with the new SKUs from the request (i.e., the old SKUs will be deleted). REMOVE_ITEMS removes the products specified in the request from the collection. REPLACE_ITEMS adds any new products to the collection and removes products that are not specified in the request. To clarify the difference: ADD_ITEMS will not remove existing products from the collection, while REPLACE_ITEMS will. Frequent use case: Drop a specific color from the linesheet: Use ADD_ITEMS action and for each product in the request exclude all SKUs with that specific color.
