以下内容应满足您的需要：

add_action (\'save_post_site-members\', \'add_term\') ;

function
add_term ($post_id)
{
    if (defined (\'DOING_AUTOSAVE\') && DOING_AUTOSAVE) {
        return ;
        }

    $meta_key = \'aab-ew-select-visible\' ;
    $tax = \'test-all-members-cpt-tax\' ;
    $term_slug = \'test-all-members-ew-tax\' ;

    $meta_value = isset ($_REQUEST[$meta_key]) ? $_REQUEST[$meta_key] : \'\' ;
    if (\'display\' == $meta_value) {
        $term = get_term_by (\'slug\', $term_slug, $tax) ;
        if ($term) {
            wp_set_object_terms ($post_id, $term->term_id, $tax, true) ;
            }
        }

    return ;
}