Magento 2 Grunt Exec Not Creating Symlinks – How to Fix

Magento2 Grunt Documentation

Install NodeJs in your pc

Use comand line:

• Install Grunt CLI tool globally

npm install -g grunt-cli

* Install the node.js project dependency

npm install

* Remove Magento Cache

php bin/magento cache:clean

* Clean compiled files by command

grunt clean

* Run CMD command prompt with administrator privilege.

grunt exec:yourthemename
grunt less:yourthemename
grunt watch

https://drive.google.com/a/green-art.ro/file/d/0B_3mauXj4AQINXVoTXlBT2JSUjA/view?usp=sharing

If that does not work grunt watch during development or run software from Php Storm roll back the following commands:
* Remove Magento Cache

php bin/magento cache:clean

* Clean compiled files by command

grunt clean

* Run CMD command prompt with administrator privilege.

grunt exec:yourthemename
grunt less:yourthemename
grunt watch

I looked into it … AND! finally the solution is too easy:

The Client Side and Grunt Compilation of *.less files REQUIRES the @import directive to contain the file extension:

use @import '_test.less' instead of @import '_test'

If ALL @imports in ALL imported files do that: you'll get a symlink to all files AND grunt watch watches! ;-)

According to: https://devdocs.magento.com/guides/v2.2/frontend-dev-guide/css-topics/css-preprocess.html#fedg_css-import