No ... all transfers from the prior year must be done when you first start the next year's return ... so either start a new return or input the info as needed in the return you already started.
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You cannot do 2018 or 2019 online now. Rather, you must purchase and install the 2018 and 2019 desktop software:
TurboTax® 2018 Tax Software for Filing Past Years’ Taxes, Prior Year Tax Preparation (intuit.com)
TurboTax® 2019 Tax Software for Filing Past Years’ Taxes, Prior Year Tax Preparation (intuit.com)
If the returns are done you can print them out to mail. If you need to finish them, you need to download the tax data file .tax2018 or .tax2019 and open them in the Desktop program for each year. If you paid for the Online version you can ask support for the Desktop download. You will need a full Windows or Mac computer to install it on.
After you get the program installed the first thing to do before you open your tax return .tax file is to update the program and install any state programs you had. Then open your file. So you first might need to start a fake return to be able to download the state program (go to FILE - NEW).
How to finish a return you started online