By help of a script you can send Shipment, Creditmemo etc emails how much you want
<?php
error_reporting(E_ALL);
ini_set('display_errors', 1);
use Magento\Framework\App\Bootstrap;
require 'app/bootstrap.php';
$bootstrap = Bootstrap::create(BP, $_SERVER);
$objectManager = $bootstrap->getObjectManager();
$state = $objectManager->get(Magento\Framework\App\State::class);
$state->setAreaCode(\Magento\Framework\App\Area::AREA_FRONTEND);
$objectManager = \Magento\Framework\App\ObjectManager::getInstance();
/** @var Magento\Store\Model\App\Emulation $emulation */
$emulation = $objectManager->create('Magento\Store\Model\App\Emulation');
$emulation->startEnvironmentEmulation(1, \Magento\Framework\App\Area::AREA_FRONTEND, true);
/** @var \Magento\Sales\Model\ResourceModel\Order\Creditmemo\Collection $shipmentCollection */
$collection = $objectManager->get(\Magento\Sales\Model\ResourceModel\Order\Creditmemo\Collection::class);
/** @var Magento\Sales\Model\Order\Creditmemo $subject */
$subject = $collection->getLastItem();
/** @var Magento\Sales\Model\Order\Email\Sender\CreditmemoSender $sender */
$sender = $objectManager->get(Magento\Sales\Model\Order\Email\Sender\CreditmemoSender::class);
$sender->send($subject);
$emulation->stopEnvironmentEmulation();
echo "Done";