Create additional short URL with custom field and 301 redirect

The first step is the rewrite rule. I’ve also added a rewrite tag so the custom query var will be parsed. You can also use the query_vars filter for this instead.

add_action( 'init', 'tipp_rewrite_rule' );
function tipp_rewrite_rule() {
    add_rewrite_tag( '%trick_nummer%', '([a-zA-Z0-9]+)' );
    add_rewrite_rule(
        '^tipp([a-zA-Z0-9]+)?',
        'index.php?trick_nummer=$matches[1]',
        'top'
    );
}

The second step is to intercept these requests, load the post, and redirect. We use the parse_request action for this, which passes a request object we can check for the presence of the trick_nummer query var.

We then create a new WP_Query to find the post with the matching value in the trick_nummer meta key, and redirect there if one is found:

add_action( 'parse_request', 'wpd_catch_tipp_requests' );
function wpd_catch_tipp_requests( $query ) {
    if( ! is_admin() && isset( $query->query_vars['trick_nummer'] ) ){
        $the_post = new WP_Query(
            array(
                'meta_key'   => 'trick_nummer',
                'meta_value' => $query->query_vars['trick_nummer']
            )
        );
        if( $the_post->have_posts() ){
            wp_redirect( get_permalink( $the_post->post->ID ) );
        } else {
            wp_redirect( home_url() );
        }
    }
}