Can you log back into the return ???   

And if you can will it not let you back into that section ?  

You will see sections for federal, state, and local under the Estimated Taxes screen -

• Log into your account and click Take Me to My Return (you must click this first)
• Use the search feature in the top right-hand corner of your screen (or search topics/bar if using desktop)
• Search for "estimated tax payments" and click the "jump to" link.  
• This will bring you right to the appropriate section to enter all of your estimated taxes paid

Or, you can also find the section by clicking on the following tabs:

• Federal Taxes
• Deductions and Credits
• You may have to click “Ill Choose what to work on” or "Show All" or "Check for More Credits" to get full list to appear
• Scroll down to Estimates and Other Taxes Paid (you may need to scroll down all the way past your "common" tax breaks list that will appear in your summary)
• Scroll down to Estimates
• Enter your 2020 Paid Estimated Taxes 

You do not edit Schedule 3 directly.  You make the changes in the TurboTax Program.  
Follow these steps:

1. Go to Deductions and Credits
2. Estimates and Other Taxes Paid
3. Estimated Tax Payments and follow the interview to change the amounts