Can I place modifiers under my size pricing modifiers?

No, you cannot nest another modifier under a size pricing option. 

When you use the size pricing strategy, the item sizes that you define (like "Small," "Medium," "Large") will appear on the Advanced properties menu editor in the same place that your modifier groups do, but it's important to note that item sizes do not function like modifiers.

 In the example above, if you add a nested modifier group under the Small or Medium size (e.g. placing "Extra Cheese" under the "Small" option), it would not display or function correctly on your POS.

If you want to offer additional choices (like toppings or add-ons) that might have different prices based on the item's size, you must add these directly to the main item itself.