I can only speak to the download version of TurboTax and don't know if the same applies to the on line version, but hopefully this will help you either way. I think the easiest way to find it without interrupting the flow of your work is to click the View tab at the top of the window, then select "Forms". A list of all of your forms will pop up. For the specific form you are using, 1040, 1040A, 1040SR, 1041, etc., click it. After the form generates on your screen, scroll down. The line specific line number varies depending on which form you are using but on one of the few lines between the section for the entry of each main form of income and your "Taxable income," you will see the bolded text for "adjusted gross income". Once you are done with that, just click the "close form" button at the bottom of the window and you should return right to where you were.
For Online, Before filing you can preview the 1040 or print the whole return. You have to pay any fees first before you can see all the forms, etc.
https://ttlc.intuit.com/community/accessing/help/how-do-i-preview-my-turbotax-online-return-before-filing/00/26160
2020 AGI is on line 11.
Hey I just found a FAQ for the current year AGI
https://ttlc.intuit.com/community/agi/help/where-can-i-find-my-current-year-agi/00/26310