Actually, I think we figured it out:
It looks like the non-editable number in the 8801 form is sourced from the "Federal Carryover Worksheet" line 21. Updating the number there changes the amount on 8801. In fact, double-clicking on the number on form 8801 line 19 takes you to that worksheet, but double-clicking on the same number in position E1 in the smart worksheet at the top of 8801 does not. This seems like a bug in Turbotax, since double-clicking on non-editable numbers usually takes you to their source location.
