nixplorer is a TUI browser for Nix derivations.
Note: This software is pretty much unmaintained, I only hack on it occasionally.
nixplorer /nix/store/something.drv
Note: These are not final.
up, down select derivation input
home select the first derivation input
end select the last derivation input
right, enter view selected derivation
left view parent derivation
y copy the selected path
page up/down scroll the environment window