If you would like to have an item in your menu for which you can freely change the name, VAT rate and price, you will appreciate the function of a variable product. You will use the function when you want to sell goods that you do not yet have at the checkout, or when your customer requests something that you do not have in the menu.
Jak správně vytvořit variabilní produkt se dočtete v tomto návodu: https://help.storyous.com/hc/en-us/articles/115001090305-CALCULATOR-FUNCTION-VARIABLE-PRODUCT