Can I revise my 2022 income tax returns by adding a parent as a dependent that I did not know I could claim?

You can amend a tax return to add a dependent.  Dependents are added in My Info.

See this TurboTax support FAQ for amending a tax return - https://ttlc.intuit.com/turbotax-support/en-us/help-article/tax-return/amend-change-correct-return-a...