This is how I deleted my unfinished return. (Beware: You probably will lose all the data you entered for that return.) I'm running 2019 Basic, downloaded, Win10.
(1) Exit TurboTax.
(2) Open File Explorer.
(3) Show hidden files/folders. From top menu: View | Options | Change folder and search options | View | Show hidden files, folders, and drives | Apply | OK.
(4) Delete the folder containing the data. Navigate to C:\ProgramData\Intuit\TurboTax\TY19. Delete the entire TY19 folder.
