The bank ROUTING number ???  

When you complete the 2020 return  AND  your return is ready to file by passing the REVIEW tab then you will be given the option in the FILE tab to enter in the current bank routing and account number BEFORE you file the return.   It cannot be done any sooner.  

You can not change it for 2019 or prior returns or for the Stimulus Check.

Your bank routing number?     You enter/edit banking information in the FILE section when you are ready to file your 2020 tax return.  You cannot change banking information for a return that you already filed.  The banking information that you enter for your 2020 return does not go from TT to the IRS until your 2020 return has been filed and accepted.  If a deposit is sent to a wrong or closed account, the bank sends it back to the IRS and then the IRS mails out a check.