The notched-support shear check landed in the engine earlier today, reachable only from a plan file. The stair card now has a field for it: write throat, or the inches of board left at the support, once the strength check above it is filled in. It saves in the plan, restores from a saved plan, and refuses a non-positive number.
Tested by reading the page source in page.test.mjs; it has not been clicked through in Chromium, and the engine side is hand-arithmetic only, not checked against a real stair or an engineer's call.