I use online TurboTax Self-Employed version. How can I do what-if scenarios for 2023 before end-year to determine how much Roth Conversion I might want to do? I want to change my 2022 tax numbers to reflect what I think they would be in 2023 to see.
TurboTax Online is not really suitable for what-if scenarios or other trial tax returns. In TurboTax Online there is only one copy of your tax return, and any change you make is saved immediately and permanently. There is no back-out or undo, and no way to exit without saving the changes. If you want to use TurboTax Online to try out different scenarios, you could use a different user ID than the one you use for your actual tax return, but you would have to do a complete new return from scratch. And you have to be careful to keep track of your different user IDs and passwords. TurboTax recommends adding "test" or something similar to the user ID to clearly distinguish it from your actual account.
If you use the CD or download TurboTax software instead of TurboTax Online you can create as many trial returns as you want, and save each one with a different file name. You can save a copy of your completed tax return with a different file name, then try out the changes in the copy without affecting your actual tax return. The CD/download software also has a What-If Worksheet that lets you easily try out different scenarios using the completed return as a starting point, but without affecting the actual tax return, and it lets you compare the scenarios side-by-side.
Another, easier way to try out different scenarios is to use the online TaxCaster calculator.