wcfm-disallow-add-delivery-person.php

add_filter('wcfm_is_allow_manage_delivery_boys', function($is_allowed) {
    if(wcfm_is_vendor()) {
        return false;
    }
    return $is_allowed;
});

add_filter('wcfm_add_new_delivery_boy_sub_menu', function($is_allowed) {
    if(wcfm_is_vendor()) {
        return false;
    }
    return $is_allowed;
});

add_filter( 'wcfm_menus', function($menu) {
    if(wcfm_is_vendor() && isset($menu['wcfm-delivery-boys'])) {
        unset($menu['wcfm-delivery-boys']['has_new']);
    }
    return $menu;
}, 301 );