Nuxtjs how to add global environment variable in all sass files
The loaders config belongs under the build property (not the root as you have it). If your project was generated with create-nuxt-app, the default nuxt.config.js already contains a build property at the bottom of the object, so you could move your loaders config into that property.
Example (tested with Nuxt CLI v2.12.2):
// nuxt.config.jsexport default { build: { loaders: { scss: { data: '$myenv: ' + process.env.MY_ENV + ';' // use `prependData` for sass-loader > 7.x //prependData: '$myenv: ' + process.env.MY_ENV + ';' } }, }}