HOW do I "generate" an amended return... will TT do it... must I do it... some other way?

I use TT2020 desktop and TT2021 desktop.

I filed my 2020 Federal return BEFORE the change that exempts the first $10,200 of UI from being taxed.  Subsequently, out of nowhere, with no explanation, I received a check form the U.S. Treasury.  My best guess is that they amended my return and issued a refund.  Given this, I know that I do NOT need to file an amended 2020 Federal return, and as such, I do NOT plan to do so.

HOWEVER, in order to (1) file an amended 2020 State return, and (2) have TT2021 “transfer-in” an accurate 2020 Federal return (when TT2021 is first launched), I need an amended/accurate 2020 Federal return.  HOW do I "generate" an accurate/amended 2020 federal return?  (1) Will TT2020 do this (when first opened)?  (2) Or must I do it manually?  (3) Or some other way?  Please advise.  Thanks.