Thank you for your reply.
I did call TurboTax support and was advised that TurboTax does not support the e-filing of California Schedule X at the moment, but that I should check again in a few months, by which time Schedule X may be supported and I can thus e-file my CA amended return.
She also told me that, since I am owed a refund, I am in no hurry to file the amended return. The deadline to e-file the amended return is Oct 15, 2021 for tax year 2020, so I will wait a few months to see I may be able to e-file via TurboTax instead of doing it the old-fashioned way.
