Someone has done just that: https://github.com/snowfallorg/nixos-conf-editor It is part of https://snowflakeos.org/, though I don’t know about its developments atm.

Nix with nix-output-monitor (nom). https://github.com/maralorn/nix-output-monitor

It shows the tree of packages to download and to build. It shortens the tree in realtime when packages have finished downloading/building and lengthens the tree when it finds more packages it needs to handle. Very fun and satisfying.

I haven’t seen this in other package managers.