Once a tax return has been filed the bank account information cannot be changed.
On your 2020 tax return if you have a tax refund or taxes are owed, for the direct deposit or direct debit you can enter the new bank routing and account number on the 2020 tax return.
When you are in the FILE section for your 2020 tax return you will be able to change your banking information. You cannot change it before then. You will not be filing a 2020 tax return until at least late January of 2021. If you are concerned about a possible second stimulus check --which Congress has not acted on -- then we hope the IRS will provide a way for you to change your banking information.