Did you try to add the one for nu as well?
packages.myVimPackage = with pkgs.vimPlugins; {
start = [
tokyonight-nvim
nvim-lspconfig
nvim-treesitter.withAllGrammars
+ tree-sitter-grammars.tree-sitter-nu
];
};
Perhaps nvim-treesitter.withAllGrammars
doesn’t include it?
Edit: I found a config on GitHub which does it like this: