related_post_query_args

You can add custom arguments via filter hook as following.

add_filter('related_post_query_args','related_post_query_args_20200126');

function related_post_query_args_20200126($args) {
    $args['s'] = 'Template'; // search term
    return $args;
}

Exclude certain post from related posts

add_filter('related_post_query_args','related_post_query_args_20200126');

function related_post_query_args_20200126($args) {

global $post;

$post_id = $post->ID;

if($post_id == 124222){
  $args['post__not_in'] =  array( 124164, 5 ); 
}

    return $args;
}