import sass variables code example

Example 1: import mixin from another file

@import "../../../theme/main.scss"

Example 2: sass @use not working

As of 8/2020 @use is only compatible with Dart Sass. 
Check compatibility with documentation.
https://sass-lang.com/documentation/at-rules/use

Example 3: sass import variable from another file

// When importing the master, you leave out the underscore, and it
// will look for a file with the underscore. This prevents the SCSS
// compiler from generating a CSS file from it.
@import "assets/master";

// Then do the rest of my CSS afterwards:
.text { color: $accent; }

// assets/_master.scss 
$accent: #6D87A7;           
$error: #811702;