You can save your current return with another name, go up to FILE - SAVE AS. Or you can delete the file directly in Turbo Tax or using Windows. To over over with a clean slate just start a new blank return, go to FILE - NEW. You can save each file with different names. They won't be combined. Just name it something you can keep track of.
For Windows,
The tax files (and PDF files) should be in your Documents then in a Turbo Tax subfolder. If you can't find them do a search for all files ending in .tax2021 or .tax2020 or .tax2019, etc.
