I am a new customer for SBA using Quickbooks. I am trying to add new bank account and need to know which tax line is most appropriate to use?

Did the SBA instruct you to go out and get a new bank account? Doubtful. Does QB track each and every expense you enter regardless of bank account? Absolutely.

Now, go ahead and get an account you will be canceling before summer is over , BUT, you do not map bank accounts to tax lines. Period. Bank accounts are asset accounts.  Transactions in and out are what are tax_mapped, not the account itself.