imaginary unit (i) position on key

[Tim Wessman]

You are right - that placement is slightly arbitrary.

The catalogs are in a row (List, Matrix, Program, Notes")
List brackets next to the list catalog.
Matrix brackets next to the matrix catalog.
" " on the Notes key.
Pi on the 3 key.
Space/underscore are together.
# is next to Base

i just sort of ended up there because there wasn't any compelling reason to place it elsewhere that wasn't already filled by something with a strong reason to be placed and it was as good a place as any of the remaining positions.