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input.scss

.some-class {
  &__some-item {
    &--active {
        color: blue;
    }
  }
}

output.css

.some-class__some-item--active {
  color: blue;
}

settings.json

{
  "sass": {
    "compiler": "dart-sass/1.32.12",
    "extensions": {},
    "syntax": "SCSS",
    "outputStyle": "expanded"
  },
  "autoprefixer": false
}