Reusing styles in SASS/SCSS without merging selectors

    %some-css {
      //CSS goes here.
    }

    .another-class {
      @extend %some-css;
    }

Could you use a @mixin?

// Define here
@mixin generic-error {
  // Error styling
}

// Replace original
.notification {
  &.error {
    @include generic-error;
  }
}