I'd say that having related values grouped and defined in this enum-manner is a
good design choice. Reduces bugs, makes code more readable and passing those
values more efficient. Wins in every category. A bunch of uncoupled constants is
more of a "lack of design" and just begs for accidental mishaps. Something like
that is common due to lack of decent enums in other programming languages.

But I'm a Nim noobie (started learning barely a month ago), so maybe somebody
else that has some good experience could verify my opinion?