This prep list is automatically created for you from a combination of 'Core Stock' items and 'Preparations'. If you mark a drink as Core Stock then it and its ingredients will appear here for prep. You can also mark single ingredients here as Core Stock as well, and again if they contain any sub-ingredients those will populate here.
The batching list is only populated by Core Stock drinks that are set to batched, for drinks made to order classics they will not appear in the batch list.
Preparations can be added and deleted however you need, allowing you to customise the list to any ingredient requirement. For each ingredient, you can add as many different Preparations as you want, which allows for multi-step items, for example: Infuse, Blend and Distill.