You appear to be using the TTax On-Line version. Unfortunately the on-line version does not support a 'what-if' scenario (that is only available with the desktop version).
Once you make ANY changes to the online version the previous information is overwritten and is PERMANENTLY deleted. You will have to manually re-enter/re-create your return.
You
might want to try to create NEW dummy accounts for your various
scenarios and then simply abandon them when you are finished.
Create New On-Line account:
turbotax.com and look for the 'New to TurboTax?" 'Start for Free' BLUE button near the top center of the screen.
How to Clear AND Delete
How to clear an on-line return and start over
https://ttlc.intuit.com/questions/1900891-how-do-i-start-over-in-turbotax-online
(Please note that the link may 'appear' to be truncated, however it will
work (if you hover your mouse over the link you will see the full link.)
How to delete tax return in TTax On-line
https://ttlc.intuit.com/questions/1899886-can-i-delete-my-tax-return-in-turbotax-online
(Please note that the link may 'appear' to be truncated, however it will
work (if you hover your mouse over the link you will see the full link.)
Note: This will also clear/delete and data your have transferred from last year or downloaded from a Financial Institution.
CAVEAT:
While you can clear the information in a return in an account, you CANNOT delete an account.
If you still want to use TTax On-Line, TurboTax's TaxCaster may be of some help
https://turbotax.intuit.com/tax-tools/calculators/taxcaster/
