Don’t use nix-env, especially if you are on NixOS (vs. NIx on another Distro).
If you need a program only once or very seldom, use nix-shell or nix run, otherwise, add it to your config.
Random getting started thread in this forum: Help me get started - Best practice, nvim, learning the language - #3 by TLATER
If you search a round a bit, you will find many more threads of this kind.