How to NoIndex All Posts in a Product Category

Hello,

Thank you for contacting Rank Math and bringing your concern to our attention. I’m sorry for any inconvenience this issue may have caused you.

You can easily do that from the product list with Rank Math PRO. Here’s a link for more information:
https://rankmath.com/kb/bulk-editing-in-rank-math/#num-3-3-set-to-noindex-pro

Here’s a screencast for your reference using Rank Math PRO:
https://i.rankmath.com/n2mnan

However, here’s a filter you can try to achieve that on your products under a category:

/**
 * Filter to set noindex to specific categories
 */
add_filter( 'rank_math/frontend/robots', function ( $robots ) {
$slugs = array();
$product_cats = wp_get_post_terms( get_the_ID(), 'product_cat' );
foreach ($product_cats as $product_cat){
    $slugs[] = $product_cat->slug;
}

if ( in_array( 'category2', $slugs ) ) {
                unset( $robots['index'] );
                $robots['noindex'] = 'noindex';
        }
        return $robots;
} );

Update the category2 to your actual product category slug.

I hope that helps.

Thank you.