You won't be able to do that in TurboTax. Now, for an anticipated stimulus check the details are still being worked out by the government at this time. We do not have information on how or if you will be able to update direct deposit information with the IRS. Once things are finalized we will be able to provide more guidance. You can also stay updated by checking back on the following links.
https://turbotax.intuit.com/coronavirus/
https://www.irs.gov/coronavirus