I forgot my username/password!
No worries! You can use this recovery tool https://myturbotax.intuit.com/account-recovery/ against any email addresses you may have used.
Be sure to close all TurboTax windows on your web browser (including this one). Then copy and paste the account recovery website link into a new web browser window and run the tool.
If none of the user ID's received will access your prior year accounts, then use the option shown in blue on the account recovery website, "Try something else."
you merge my online accounts?
Sounds like you may have multiple accounts. Read below on how to determine if so, https://ttlc.intuit.com/replies/3302270.
I create another return online?
Great question! You don’t want to overwrite your current information but you can create up to 5 accounts with the same email address. Follow the steps in the FAQ below. https://ttlc.intuit.com/replies/3288574