Here are some features that I think will be a good addition for this project
An export command that similar to distrobox-export. You should type nix-portable nix-export --app firefox for app icons export or nix-portable nix-export --bin firefox --export-path ~/.local/bin
System wide configs for flake.nix, flake.lock, and default.nix that are located in /etc/nix-portable. They are read when nix-shell is executed. If the files exist, nix-shell will install programs that are listed on default.nix. Nix portable doesn't create the files, the user must put them in /etc/nix-portable.
Here are some features that I think will be a good addition for this project
nix-portable nix-export --app firefox
for app icons export ornix-portable nix-export --bin firefox --export-path ~/.local/bin