question

I believe there may be a disconnect here concerning our overall architecture surrounding items, categories, and modifiers.

A simplistic breakdown of how the three are related:
- An item can belong to a category, a category can have many items
- A modifier belongs to a modifierGroup, a modifierGroup can have many modifiers
- An item can have many modifierGroups, a modifierGroup can have many items


In terms of associations:
- An item can be associated with a category.
- A separate association can be made between the item and a modifierGroup.
- When an Item has been associated with a modifierGroup, you can then apply any of the modifiers from the modifierGroup to said item. (based on the rules prescribed to the modifier group - minRequired, maxAllowed)

*Note: there is no association between categories and modifierGroups


In practice:
To make your toppings modifiers, rather than items, you could adhere to an inventory structure like following:
- Create an item ("Pizza")
- Create a Modifier Group ("Vegetable Toppings")
- Create a modifier for each topping ("Peppers", "Olives", "Mushrooms"...etc)
- Make an association between the item ("Pizza") and the modifierGroup ("Vegetable Toppings")

*Note: Once the associations is made you can now add the modifiers ("Peppers", "Olives", "Mushrooms"...etc) from the modifierGroup ("Vegetable Toppings") to that item ("Pizza") and the modifiers will not show up as whole inventory items.

I hope this is helpful! Please let me know if any of this is unclear.