How are chargeback fees handled?

The dispute fee goes on the transaction costs line, with your other payment fees, because that is what it is. The disputed amount itself is treated as a return, since the money went back to the customer.

What a chargeback does not trigger is return processing. No parcel comes back, so charging a return label and a restocking cost against it would invent work that never happened. That distinction is one of the small rules that keeps the logistics line honest.