How to add same product to cart twice instead of changing quantity in WooCommerce

Add this to your theme’s functions.php file

function lpj_add_prod_as_separate_cart_item( $cart_item_data, $product_id ) {
  $unique_cart_item_key = uniqid();
  $cart_item_data['unique_key'] = $unique_cart_item_key;

  return $cart_item_data;
}
add_filter( 'woocommerce_add_cart_item_data', 'lpj_add_prod_as_separate_cart_item', 10, 2 );