To give my 2 cents as someone who spent a few years using Nix (via NixOS) day to day, I think it would be complementary to the kind of deps management discussed here.
For libraries that are easily distributed as JARs, Nix doesn't add much because JVM class loading takes over anyway (at least, if you include Maven and co's management which is relatively reliable). For anything that depends on something "foreign" (e.g might require shared library loading, dynamic linking, external binaries, anything a more specialized tool won't understand), Nix is excellent at creating an environment where that shared resource is where you need it no matter what.
For example, Nix would shine when it comes to ensuring the right version of say GraphViz is available for rendering state graphs. The main caveat is that to use Nix at all you need Nix installed alongside its own versions (and install scripts / "derivations") of any dependencies you need, which can be kinda inconvenient if you're not committed to using it. Not invasive mind you - it can just sit in your home folder - but heavier than some solutions.
-Finn