The year-over-year comparison can be found in TurboTax Online by going to "Tax Home" on the left-hand side menu and selecting Review then Year Over Year Comparison. The year-over-year comparison only shows the current tax year and the previous tax year.
Also be aware that the year-over-year comparison is only available if you transferred your previous year's return into your current year's return.

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I am trying to do this ,but my index of topics from the left hand sign has not appeared at all.Please help.Do I need to contact technicalsupport.?Never been a problem B4. thank you Heather Manson

If you transferred your 2023 info into your 2024 return, then the year over year comparison is in the Review section after the page where you certify your info. There is no way to go directly there.