We do have the same issue. The proposed vendor changes workflow that has been introduced only covers changing the default bank account on the vendor master sheet but it doesn't pick up when details are changed on an existing bank account or a new bank account that isn't the default one is being added.

We found the following ways to bypass it:
Ways to bypass it:
1.) Change default bank account on supplier account, then change bank details after workflow has been approved
2.) Have a bank account on the supplier that defaults into transaction approved by workflow (PO header, vendor invoice journal line, general journal line) and change it to another, unapproved bank account on the transaction before posting
3.) Have a bank account on the supplier that defaults into transaction approved by workflow (PO header, vendor invoice journal line, general journal line) and change it to another, unapproved bank account on the open supplier transaction
4.) Change the supplier bank account on the payment journal/payment proposal to an unapproved bank account record on the same supplier

Therefore the need to provide a control for creditor bank accounts continues to be addressed by cumbersome workarounds only.