I think a prior message claimes that grass, leaves and wood chips would
draw nitrogen. Did I get that right ?

For a garden in 6b zone is there any crop that's worth planting after the
last tomato has been picked ?

Supplemental nitrogen can easily be added to make up for any shortfall
the current crop requires.

If you have a nurse bed of lettuce and cruciferous vegetables you can
transplant them into the tomato plot for a fall crop. Time for
radishes from seed and perhaps mesclun.
A few bales of hay and some plastic sheeting and you can extend the
growth and the harvest well into winter.