I can't enter numerical values in the W-4 federal income tax withheld section. This number is pre-populated and can't be changed. Estimate tax values can be changed.

Are you referring to your W-2? The W-4 form is filed with your employer and not a part of your tax return.

I am having the same issue.  I am filling out a W4 form to adjust withholding for this year 2020.  When I try to enter a value for Federal Income Tax already withheld there is a place to fill the value in, but when I type nothing is entered.  I have relaunched the application, but I still have the same issue.  I can enter values other places during the process.  

Hi I having the same issue - I am trying to update my w-4 to give to my employer but can't update the fed income tax withheld number...any help you can provide please? thanks