You have to set up a separate account if you want to file another return using TurboTax Online. You will need to create a completely separate login for that person.
TurboTax has a download product that includes up to 5 federal filings. Here's the link to that:
Online is only good for 1 return. But you can use the same email address for 5 accounts. How to start another return in the Online version https://ttlc.intuit.com/replies/3288574
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