"NODE_ENV" is not recognized as an internal or external command, operable command or batch file

It sounds like your error comes from an attempt to run something like this (which works in Linux)

NODE_ENV=development node foo.js

the equivalent in Windows would be

SET NODE_ENV=development
node foo.js

running in the same command shell. You mentioned set NODE_ENV did not work, but wasn't clear how/when you executed it.

I wrote a module for this: win-node-env.

It creates a NODE_ENV.cmd that sets the NODE_ENV environment variable and spawns a child process with the rest of the command and its args.

Just install it (globally), and run your npm script commands, it should automatically make them work.

npm install -g win-node-env

for windows use & in between command also. Like,

  "scripts": {
    "start": "SET NODE_ENV=development & nodemon app/app.js",
  }