Hi
I know how to type several Unicode characters for my user-defined variable names (i.e. x_1[TAB] for subscripted x indexed by 1), but I would like to know why it is not possible to type, in the REPL, G_N[tab] for Newton’s gravitational constant? Why are some subindices allowed and others not? In particular, I tried the UnicodeREPL.jl package with no success…
As far as I know, the reason is simple: a Unicode subscript N just does not exist. This Wikipedia page contains an overview of the existing super- and subscript characters in Unicode. Note that also e.g. b and y are missing as subscripts (though are included as superscripts).