@SameSameButDifferent If you paid for the Online version you can ask them to give you the Desktop program (unless you used the Online Free edition).
To amend you need to download the tax data file ending in .tax2023 and open it in the program.
Save the tax file, scroll down to I need my tax file to Amend
https://ttlc.intuit.com/community/saving/help/how-do-i-save-my-turbotax-online-return-as-a-tax-data-...
How to Amend a prior year
https://ttlc.intuit.com/community/amending/help/how-to-amend-change-or-correct-a-return-you-already-...
