For 2020? Do you mean 2021? Are you using the Online version or the Desktop program?
To compare Joint to MFS. If you are using the Online version, do NOT change anything on your return. You would have to start with a new account and do a test return. You don't have to pay unless you want to print it out. So you might need 3 accounts, one for Joint and two MFS, one for each spouse.
How to start another return in the Online version
https://ttlc.intuit.com/community/using-turbotax/help/how-do-i-start-another-return-in-turbotax-onli...
It would be better to use the Desktop CD/Download program. It can do unlimited returns and has a What If worksheet to compare them and many other advantages over the online version. You can move your current online return to the Desktop program without paying for Online.
You can buy the Desktop CD/Download program here
https://turbotax.intuit.com/personal-taxes/cd-download
If you are using the Desktop program……
You probably will have to fill out 3 new returns. The 2 MFS returns will have different data to enter. Well you could fill out 1 of the MFS returns first (whoever you want to be listed as Primary). Then copy it, go up to FILE - Save As and give it another name and then change it to Joint and add the other spouse to it. Then you have to start a new blank return to do the other spouse's MFS return.
