When it asks to transfer you can browse to where 2020 is. I think you can use use Finder to find it. It might be buried somewhere.
How to transfer into Mac Desktop
https://ttlc.intuit.com/community/tax-data-file/help/how-do-i-transfer-last-year-s-return-into-the-t...
How to find tax files on Mac
https://ttlc.intuit.com/community/tax-data-file/help/find-your-tax-data-file-in-mac/00/26206
