Preferred payment method can be set in the Customer Hub and Customer Portal. On the Customer Hub go to Configuration -> Payment Methods and set a preferred payment method in the settings (click on the sub-menu "...")
On the Customer Portal go to the Payment Methods tab.
A preferred payment method will have a Preferred chip next to its name. Please note that only one preferred method can be selected for cards/direct debits. If you want to set another one, you’ll need to unmark the preferred first.
