I accidentally bought TurboTax 2023 for desktop instead of online. I have the license #, can that be used for online? I've always done online and want to do it again!

No you cannot use the license code for online TurboTax.  The pricing structure is very different for online and the CD/download.  You can request a refund for the desktop software and then pay to use online.

To request a refund from TT ;  https://support.turbotax.intuit.com/forms/refund-request.jsp

They don't automatically transfer, and the pricing is different.  Just start using TT Online, you only pay the fee when you are ready to file.   Meanwhile, use the 60 day money back guarantee to get a refund of the price you paid for the desktop program.

https://ttlc.intuit.com/turbotax-support/en-us/help-article/intuit-account-billing/turbotax-satisfaction-guaranteed-refund-policy/L7kHGYVl8_US_en_US

Or, you might be able to transfer the activation, but you would have to call customer support.