How do I override the Military Benefits Subtraction rule for VA on TurboTax since it is not consistent with state law (https://www.tax.virginia.gov/military-benefits-faq)

The program has not yet been updated to include those under 55.  This is generally because the state has not made all the up dates to their forms.  Once they make all the updates to their forms, then TurboTax will make the updates to the program.  The forms availability list does not mention an update time for this, so it would be best to check every few days to see if the updates have been made.  It should be done by late January or early February.

If you are using the desktop version, you can go to forms mode and make the changes on the forms directly.  If you are using the online version, there is no way to override what is being entered.