1. Modifiers Settings (Business: General) must be Recipe Swaps or Notes & Recipe Swaps; with any other value swaps are not even saved when you press Save on the meal.
2. Each substitute needs its active toggle on and a quantity greater than 0 for the portion the customer is ordering.
3. The parent ingredient must itself have a quantity on that portion, and the portion must be active.
4. Save the meal after changes - swap settings only persist on Save.

If you only want a free-text note box for customers, choose Notes.