No. The only way to downgrade is to clear your tax return and start over. See the following FAQ.
Can I downgrade to a lower-priced version of TurboTax Online?
Basic? Basic is a Desktop CD/Download program. The Free Edition is the version below Deluxe in Online.
To go back to the Free Edition or a lower version you can try to clear and start over https://ttlc.intuit.com/community/using-turbotax/help/how-do-i-clear-and-start-over-in-turbotax-online/00/26444
In the regular Turbo Tax Free Edition, information that you can enter is limited now. Why do I have to upgrade from the Free Edition?
https://ttlc.intuit.com/community/upgrading/help/why-do-i-have-to-upgrade-from-free-edition/00/26379
OR There is also The Turbo Tax Free File program which is free for federal and state. And has more forms than the Federal Free Edition, like Schedules A, B, C , D, E, F, EIC, H, K-1, SE, etc.
To qualify for the Free File website you just need to meet one of these 3 things
AGI $39,000 or less
Active duty military with AGI of $72,000 or less
OR qualify for EIC (earned income credit.)
In order to use the Free File program, you have to start it at a special website. Click on Sign in at the top right. It may let you continue your return so you don't have to start over.