First can you explain why you need order tagged event?
I assume this is an automatic discount and not manually applied? Maybe we can find a better method for these discounts.
Because the client uses order tag based discount features. Different products have different rates that belong to D1, D2, D3 or D4 discount type.
It also has a use case where Customers get a discount on products but have to pay for add-ons i.e. order tag add-ons.
But staff get a discount on products and on add-ons.