With the new addCustomItemsToCart( ) API you can add simple, custom items to the cart that will be reflected in the total price.
This is especially useful when you want to allow a site-visitor to add an item that is not exactly a “product” to the cart. For example, extra insurance or an agent’s fee.
Learn more at https://www.wix.com/corvid/reference/wix-stores/addcustomitemstocart