If you try to change a category in an Online Banking transaction (transaction automatically imported into an Online Banking account), MoneyWiz will ask you if you want to change the category for all transactions with this payee with available options:
Change all -- this will change the category for all transactions that have the same payee & category pair.
Change only this one -- will only change this one transaction, leaving all others unaffected.
Cancel -- will make no changes.
It's important to note that MoneyWiz will remember your choice and next time a transaction with that payee will be imported, MoneyWiz will select the category you've chosen.