Index 10Web Gallery Titles | WordPress.org

Looks like the 10Web Photo Gallery shortcode is only active in the front end. When Relevanssi indexes the post, the gallery shortcode is indexed as is, un-expanded. This means Relevanssi can’t see what’s inside the gallery.

You can try adding this to your site:

add_filter( 'relevanssi_post_content', function( $content ) {
    $bwg = BWG();
    add_shortcode( 'Best_Wordpress_Gallery', array( $bwg, 'shortcode' ) );
    return $content;
} );

Then rebuild the index. Does that help?

Adding your filter did work. Thank you for this very quick solution.