A part of the UK A-Level Physics specification, inclusion of the atomic mass constant (1.660 539 068 92 x 10-27 kg according to CODATA 2022 recommended values) would be particularly useful to students. Other calculators e.g. CASIO CG50 include this constant. Numworks already includes constants mp and mn, this would complete the set of constants needed for the Nuclear Physics topic.
Additional context
https://physics.nist.gov/cgi-bin/cuu/Value?u