Multiple EFT banks can be added to a Vendor record on the EFT Bank Information tab. When the first is added, the status is marked as EFT but any additional banks are marked as Inactive.
Only one EFT bank can be active at a time. If you need to alternate between multiple banks, you would need to open the new bank from the vendor record and change the status to EFT. That will change the first bank to Inactive.