No you can not open or import or move a current year tax file ie: .tax2020 from your computer back to the Online version. You can only go the other way, from Online TO Desktop. But you can Transfer the .tax2020 file into next year's Online version.
See my answer on your other post here,
https://ttlc.intuit.com/community/after-you-file/discussion/re-how-import-prior-years-returns-new-co...
