There are some physical constant data in Mathematica, but they do not seem to include the examples Artur lists:
AssociationMap[#["Symbol"] &,
EntityList@Entity["PhysicalConstant"]](*//DeleteMissing*)
Also, many of the constants are missing a symbolic representation.
Artur, I don't know how W|A decides on the constant symbols it uses. There may be no complete list per se, but if not, maybe Wolfram could generate and publish such a list. W|A seems incomplete without such information.
