See this TurboTax support FAQ for downloading the tax data file from the 2019 online edition and continuing the 2019 tax return using the 2019 desktop software - https://ttlc.intuit.com/community/saving/help/how-do-i-save-my-turbotax-online-return-as-a-tax-data-...
And then how do I transfer the downloaded file back to the Turbo Tax software?
After you install the TurboTax software on your personal computer, you start the program and then click on File at the top left of the desktop program screen. Click on Open Tax Return. The software will look for the tax data file you downloaded from the online edition. If not found then you can browse to the location where you downloaded the file.