I'm filing my federal refund. I selected the option "Direct deposit (standard timing)" but I'm unable to change the bank account on file. How can I add a new account?

You have to go to Step 2 in the FILE section.

 

HOW TO CHANGE OR ENTER BANKING INFORMATION FOR REFUND

https://ttlc.intuit.com/turbotax-support/en-us/help-article/tax-refund/change-transferred-direct-deposit-information/L77NCbU6D_US_en_US?uid=m6tuh572

 

 

You cannot  change banking information while your return is in pending, nor can you change it after the return is accepted.  The IRS does not allow it.