Turns out that I wasn't actually importing the file originally, but instead just hardcoding it in overlays/default.nix I changed the overlay in neovimOverlay.nix however as overlays/default.nix didn't actually import neovimOverlay.nix, but instead hardcoded it's contents, obviously nothing happened. This is now fixed.
SCDIKI3JG3AOMEQUIX4CDOYRJH2VOWYBO5PZBDQMETW4RZOR676QC #import ./neovimOverlay.nix#import ./discordOverlay.nix(self: super:{#discord = super.discord.overrideAttrs (_: {# src = builtins.fetchTarball {# src = "https://discordapp.com/api/download?platform=linux&format=tar.gz";#}});})(self: super: {neovim-unwrapped = super.neovim-unwrapped.overrideAttrs (oldAttrs: {version = "01-27-2021";src = self.fetchFromGitHub {owner = "neovim";repo = "neovim";rev = "52ca7f1a26e4da95f3b3b00670252cfdf788a011";sha256 = "1970c4yrbfcwa2nnf3wjzaic7n6dplz786ns40sf5saj0nkqp7hj";};buildInputs = (oldAttrs.buildInputs ++ ([ self.tree-sitter ]));cmakeFlags = oldAttrs.cmakeFlags ++ [ "-DUSE_BUNDLED=OFF" ];});})
(import ./neovimOverlay.nix)(import ./discordOverlay.nix)#(self: super:# {# discord = super.discord.overrideAttrs (_: {# src = builtins.fetchTarball {# src = "https://discordapp.com/api/download?platform=linux&format=tar.gz";# }});# })