How do I go into my 2023 tax return program that I have already filed and look at the details of a line item? (I can only see the pdf.)

Did you use the Online program?  

You would have to download the .tax2023 data file and install the 2023 Desktop program to open it to see the actual entries.  If you paid for Online you can ask for the Desktop program.   You can download the tax file for free.  Then you need to install the Desktop program.  But they only have the Desktop download program for the last 3 years.

After you get the program installed the first thing to do before you open your tax return .tax file is to update the program and install any state programs you had. Then open your file. So you first might need to start a fake return to be able to download the state program (go to FILE - NEW).

If you didn't pay for the Online version you will have to buy the Desktop program download.  You can buy the last 3 years of Turbo Tax here,

https://turbotax.intuit.com/personal-taxes/past-years-products/

You will need a full Windows or Mac to install it on.

Save the tax file

https://ttlc.intuit.com/community/saving/help/how-do-i-save-my-turbotax-online-return-as-a-tax-data-file/00/25740