Add a new class on an specific position

input.scss

// Desired output
// .woocommerce-page.single-product main .product_cat-intentional-pause form.cart #wc-stripe-payment-request-wrapper

.woocommerce-page.single-product {
  main {
      form.cart {
            #wc-stripe-payment-request-wrapper {
                
                $selector: nth(&,1);  // Current element
                $grandparent: nth($selector, -2); // Grandparent selector
                
                $grandparent-pos: index($selector, $grandparent);
                $new-grandparent: set-nth($selector, $grandparent-pos, '.extra-class form.cart');
                
                @at-root #{$new-grandparent} {
                    color: red;
                }
            }
        }
    }
}

output.css

.woocommerce-page.single-product main .product_cat-intentional-pause form.cart #wc-stripe-payment-request-wrapper {
  color: red;
}

settings.json

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