This mostly worked. But ...
- This appears to have worked very well for the Federal 1040.
- However, it appears that any excess above the $600 is not forwarded to my Colorado state return, where it would have been allowed as an additional deduction. Some experimentation shows that once the amount goes above $600 in the Federal form any excess is NOT forwarded to the Colorado form because there is no change to the Colorado tax amount.
- So I'm going to guess the additional step for filers in states that allow deductions above the Federal limit is to manually determine the excess from the federal form, then add any "additional deduction" the state may allow, then input that in the state form. In the case of Colorado this total additional amount goes in the box in the "Additional Qualifying Charitable Contributions" page. Without any visible worksheets I can't tell if something is being counted twice, but that doesn't appear to be the case.
With this additional note your solution appears to be the best for those taking the Standard Deduction plus claiming the cash deduction on Federal and additional allowed deductions on the State form.
