Save the WooCommerce product_cat details meta field passed by the add or edit category page

functions.php

<?php

add_action( 'create_product_cat', 'wpm_product_cat_details_meta_save' );
add_action( 'edit_product_cat', 'wpm_product_cat_details_meta_save' );
/**
 * Save Product Category details meta.
 *
 * Save the product_cat details meta POSTed from the
 * edit product_cat page or the add product_cat page.
 *
 * @param  int $term_id The term ID of the term to update.
 */
function wpm_product_cat_details_meta_save( $term_id ) {

	if ( ! isset( $_POST['wpm_product_cat_details_nonce'] ) || ! wp_verify_nonce( $_POST['wpm_product_cat_details_nonce'], basename( __FILE__ ) ) ) {
		return;
	}

	$old_details = get_term_meta( $term_id, 'details', true );
	$new_details = isset( $_POST['wpm-product-cat-details'] ) ? $_POST['wpm-product-cat-details'] : '';

	if ( $old_details && '' === $new_details ) {
		delete_term_meta( $term_id, 'details' );
	} else if ( $old_details !== $new_details ) {
		update_term_meta(
			$term_id,
			'details',
			wpm_sanitize_details( $new_details )
		);
	}
}