You can only transfer a prior year return into your current return.  You can use the Desktop software and then transfer your 2021 tax return into your 2022 return.  You cannot switch the 6 years of Online returns into your Desktop software.

How do I switch from TurboTax Online to TurboTax CD/Download?

https://ttlc.intuit.com/turbotax-support/en-us/help-article/intuit-product-orders/switch-turbotax-on...