Any meal recipe of your kitchen can be added; the picker hides inactive meals by default, and meals marked inactive later stay on the menu with an INACTIVE - prefix. For portion sizes, a meal can only be added with the default portion or with portion sizes that are configured on the meal itself (Meals > edit meal > Portions) - those are the options shown under Select Portion Sizes. The CSV upload enforces the same rule (Portion Size #N is not valid for meal #M). Each meal/portion combination is its own line with its own Quantity Needed, stock and alert.