Doesnt look like thats an option.  Maybe @itonewbie  can confirm.

https://proconnect.intuit.com/community/proconnect-tax-online-discussions/discussion/how-to-import-a...

Yes, you can import TurboTax's 2018 file to proforma the client's 2019 return.  See these articles for how the conversion process works and what will convert for 1120.

https://proconnect.intuit.com/community/help-articles/help/proconnect-tax-online-conversion-informat...

https://http-download.intuit.com/http.intuit/CMO/proadvisor/ito/pdf/TurboTaxConvertedItems.pdf

@Just-Lisa-Now-This is a slightly different question since what the OP wants to do is consistent with the normal conversion process whereas the other question is about converting a 2019 TurboTax return to a 2019 PTO return.