Skip a certain category from being indexed as a facet

functions.php

<?php
function cm_tsfwc_20220404_skip_product_category( $formatted_data, $raw_data, $object_id ) {
	$categories     = get_the_terms( $raw_data->get_id(), 'product_cat' );
	$category_names = [];
	if ( ! empty( $categories ) ) {
		foreach ( $categories as $category ) {
			$parents_ids = get_ancestors( $category->term_id, 'product_cat' );
			array_unshift( $parents_ids, $category->term_id );
			foreach ( $parents_ids as $parent_id ) {
				//replace 29 with the id of product category you do not want to index
				if($parent_id == '29'){
					continue;
				}
				$term             = get_term_by( 'id', $parent_id, 'product_cat', 'taxonomy' );
				$category_names[] = html_entity_decode( $term->name );
			}
		}

	}
	if ( ! empty( $category_names ) ) {
		$formatted_data['category'] = is_array( $category_names ) && ! empty( $category_names ) ? array_values( array_unique( $category_names ) ) : [];
	}

	return $formatted_data;
}

add_filter( 'cm_tsfwc_data_before_entry', 'cm_tsfwc_20220404_skip_product_category', 10, 3 );