the desktop app does have forms mode by which you can skip the interview process (step-by-step mode) or you can switch back and forth. in forms mode, you see what looks like the actual forms and you can enter numbers or other data. some lines may be computed so do not override them. That can lead to erroneous results. the more you enter the more that can be transferred to the next year. the 1040 itself comes from other entries on other forms. regardless of the mode used, other than the data transferred it's like preparing the returns from scratch.
say you have 3 - 1099-int for 2018. you could use a dummy name and do the math to enter just the total in one 1099-int rather than creating 3. but then when you do 2020 only that one 1099- will transfer. the issue I see is making sure 2019 and 2020 reflect what was filed so that 2021 is correct.
you can get actual copies of the tax returns you filed for 2019 and 2020 by filing form 4506 with the IRS (no state data) theres a fee of $43 per return or you can get transcripts online after registering or requesting them with form 4506-T - free
https://www.irs.gov/forms-pubs/about-form-4506
https://www.irs.gov/individuals/get-transcript
https://www.irs.gov/pub/irs-pdf/f4506t.pdf
if you prepared '19 and '20 on your desktop, there is a backup file that starts with a ~. it's in the same folder as the .taxXXXX file.
it might not be corrupt. if you still have the desktop app for that year installed, it should open by double-clicking on it. then you can save it under some other name.
