nixpkgs ships with a tlaplus package which contains some standalone tools like tla2tex and tla2any etc but for the entire IDE I had to come up with my own package. I haven't submitted it upstream yet as the layout of the package dir is entirely wrong so I need to work on that first but it works for far.

tlatoolbox.nix

{ stdenv, fetchurl, gtk2, xorg, patchelf, unzip, makeWrapper, jre }:
let version = "1.5.6"; in
stdenv.mkDerivation rec {
  inherit version;
  name = "TLAToolBox-${version}";

  src = fetchurl {
    url = "https://tla.msr-inria.inria.fr/tlatoolbox/products/TLAToolbox-${version}-linux.gtk.x86_64.zip";
    sha256 = "1b5sf4d7sv0x1hg4f1if3q7wzsi09dr8fv71qfagj8m25zrh3lvj";
  };

  buildInputs = [ patchelf unzip makeWrapper jre ];

  unpackPhase = ''
    unzip $src
  '';

  buildPhase = ''
    patchelf  --set-interpreter "$(cat $NIX_CC/nix-support/dynamic-linker)" ./toolbox/toolbox
  '';

  installPhase = ''
    mkdir -p $out/bin
    cp -r toolbox/* $out
    wrapProgram $out/toolbox \
      --set JAVA_HOME "${jre}" \
      --prefix PATH : "${jre}/bin" \
      --prefix LD_LIBRARY_PATH : ${stdenv.lib.makeLibraryPath [ gtk2 xorg.libXtst ]}
    ln -s $out/toolbox $out/bin/tlatoolkit
  '';
}