If you want to use a different account for payments with Hacienda, you will have to:
Log in > Banking > Add bank account
Once added, from the points menu select "Use this account for payments with Hacienda".
It will then be marked as "Selected account for payments with Hacienda".
That's it! Your taxes will be paid by direct debit to this account.
⚠️Please note that this account must have a Spanish IBAN and that you must change it before the start of the tax reporting period for that quarter.