You're in the right place, @Paul C1.
You can run a Profit and Loss Comparison report to compare 2019 and 2020, however showing them as a percentage isn't supported at this time. To run the comparison report, follow these quick steps.
That's it! For more information on customizing your reports further, you can check out: Customize reports in QuickBooks Online
Shoot me a reply if you have any other questions. I'm determined to be your number one resource for QuickBooks Online. Have a wonderful day!