I need to recalculate my 2020 estimated taxes since I won't have an MRD withdrawal this year. Where/how I can find a tool here to do this?

I filed my taxes in March, before the gov't said it won't be necessary to take an MRD from a retirement account in 2020.  So the TT calculation includes that amount.  I want to recalculate the estimate tax without the MRD amount.
The only info I've found in TT Help doesn't seem to apply Turbo Tax Online.  When I try to access my return, the only option I get is to download it.  (I already did that.)  Any suggestions would be appreciated.