Limit sale flash by category or ID - Limit the categories or products where the WooCommerce sale flash is displayed. https://www.damiencarbery.com/2018/10/limit-sale-flash-by-category-or-id/

limit-sale-flash-by-category-or-id.php

<?php
/*
Plugin Name: Limit sale flash by category or ID
Plugin URI: https://www.damiencarbery.com/2018/10/limit-sale-flash-by-category-or-id/
Description: Limit the categories or products where the WooCommerce sale flash is displayed.
Author: Damien Carbery
Author URI: https://www.damiencarbery.com
Version: 0.1
*/


add_filter( 'woocommerce_sale_flash', 'dcwd_limit_wc_sale_flash', 10, 3 );
function dcwd_limit_wc_sale_flash( $markup, $post, $product ) {
	$exclude_by_product = array( 33 );  // List of product IDs where sale flash will not be shown.
	$exclude_by_category = array( 'hoodies' );  // List of category slugs where sales flash will not be shown.
	
	if ( in_array( $product->get_id(), $exclude_by_product ) ) {
		//return 'Product Excluded';  // Use this during testing to ensure code works.
		return '';
	}
	
	// Get product's categories.
	$product_categories = get_the_terms( $post->ID, 'product_cat' );
	if ( $product_categories && ! is_wp_error( $product_categories ) ) {
		foreach ( $product_categories as $category ) {
			if ( in_array( $category->slug, $exclude_by_category ) ) {
				//return 'Category Excluded';  // Use this during testing to ensure code works.
				return '';
			}
		}		
	}
	
	return $markup;
}