Can the saved 2023 return be used to estimate any additional tax in 2024 based on projected increases in earnings?

[BillM223]

If you are using the Online product, this can be hazardous, because you can have only one set of tax data for an account. If you make changes to the numbers in your "real" tax return, unless you are extremely careful, TurboTax will end up remembering your made-up numbers next year.

In this case, it would be safer to create a second Online TurboTax account and reproduce the numbers there - that way, it won't matter if you lose track of what you are doing, because your original tax data will still be there.

If you use the desktop software, on the other hand, you can have up to 5 tax returns at a time (saved under different names on your PC). This is the easy and safer way to do tax planning (of course, this means that you would have to buy the desktop software).

[VolvoGirl]

Yes.    Turbo Tax will automatically calculate the 1040ES estimated payments.  I don't know if that section is ready yet.  
https://ttlc.intuit.com/community/tax-payments/help/can-turbotax-calculate-next-year-s-federal-estim...

To prepare estimates for next year you need to be in your current return. But be careful not to change anything in your actual return.

In TurboTax Online, sign in to your account.
Select Tax Home in the left menu.
Scroll down to Your tax returns & documents.
Select 2023, and then select Add a State (you're not actually adding a state, this just gets you back into your return so you can make changes).

Go here,
Federal Taxes or Personal (Home&Business version)
Other Tax Situations
Other Tax Forms
Form W-4 and Estimated Taxes - Click the Start or Update button

Say No to W4. When you get to the W4 and Estimated Taxes section, say you want to adjust your income to go though all the screens.

[Macan]

Thank you to both Bill and Volvo for the how-to instructions.  Will give it a try in a couple of months.

Be well.