Magento Custom Confirmation Email Template – Password Not Displaying

cc function existed in zend_mail class in lib folder.

public function addCc($email, $name='')
        {
            if (!is_array($email)) {
                $email = array($name => $email);
            }

            foreach ($email as $n => $recipient) {
                $this->_addRecipientAndHeader('Cc', $recipient, is_int($n) ? '' : $n);
            }

            return $this;
        }

For now i just edited core files.but we need to override to our local/community folder.I have created 2 arrays & 4 new functions for cc in info.php

<?php
class Mage_Core_Model_Email_Info extends Varien_Object
{
    /**
     * Name list of "Bcc" recipients
     *
     * @var array
     */
    protected $_bccNames = array();
    protected $_ccNames=array();

    /**
     * Email list of "Bcc" recipients
     *
     * @var array
     */
    protected $_bccEmails = array();
    protected $_ccEmails = array();
    /**
     * Name list of "To" recipients
     *
     * @var array
     */
    protected $_toNames = array();

    /**
     * Email list of "To" recipients
     *
     * @var array
     */
    protected $_toEmails = array();


    /**
     * Add new "Bcc" recipient to current email
     *
     * @param string $email
     * @param string|null $name
     * @return Mage_Core_Model_Email_Info
     */
    public function addBcc($email, $name = null)
    {
        array_push($this->_bccNames, $name);
        array_push($this->_bccEmails, $email);
        return $this;
    }
 public function addCc($email, $name = null)
    {
        array_push($this->_ccNames, $name);
        array_push($this->_ccEmails, $email);
        return $this;
    }
    /**
     * Add new "To" recipient to current email
     *
     * @param string $email
     * @param string|null $name
     * @return Mage_Core_Model_Email_Info
     */
    public function addTo($email, $name = null)
    {
        array_push($this->_toNames, $name);
        array_push($this->_toEmails, $email);
        return $this;
    }

    /**
     * Get the name list of "Bcc" recipients
     *
     * @return array
     */
    public function getBccNames()
    {
        return $this->_bccNames;
    }

    /**
     * Get the email list of "Bcc" recipients
     *
     * @return array
     */
    public function getBccEmails()
    {
        return $this->_bccEmails;
    }
/**
     * Get the name list of "cc" recipients
     *
     * @return array
     */
    public function getccNames()
    {
        return $this->_ccNames;
    }

    /**
     * Get the email list of "Bcc" recipients
     *
     * @return array
     */
    public function getccEmails()
    {
        return $this->_ccEmails;
    }
    /**
     * Get the name list of "To" recipients
     *
     * @return array
     */
    public function getToNames()
    {
        return $this->_toNames;
    }

    /**
     * Get the email list of "To" recipients
     *
     * @return array
     */
    public function getToEmails()
    {
        return $this->_toEmails;
    }
}

In Mage_Core_Model_Email_Template_Mailer

public function send()
    {
        $emailTemplate = Mage::getModel('core/email_template');
        // Send all emails from corresponding list
        while (!empty($this->_emailInfos)) {
            $emailInfo = array_pop($this->_emailInfos);
            // Handle "Bcc" recepients of the current email
            $emailTemplate->addBcc($emailInfo->getBccEmails());
            $emailTemplate->addCc($emailInfo->getccEmails());
            // Set required design parameters and delegate email sending to Mage_Core_Model_Email_Template
            $emailTemplate->setDesignConfig(array('area' => 'frontend', 'store' => $this->getStoreId()))
                ->sendTransactional(
                $this->getTemplateId(),
                $this->getSender(),
                $emailInfo->getToEmails(),
                $emailInfo->getToNames(),
                $this->getTemplateParams(),
                $this->getStoreId()
            );
        }
        return $this;
    }

add this function in Mage_Core_Model_Email_Template

public function addCc($cc)
    {
        if (is_array($cc)) {
            foreach ($cc as $email) {
                $this->getMail()->addCc($email);
            }
        }
        elseif ($cc) {
            $this->getMail()->addCc($cc);
        }
        return $this;
    }

In Helloworld/Custom/Model/Observer.php file, i think you need change

public function __construct(
    \Magento\Framework\App\Config\ScopeConfigInterface $scopeConfig,
    \Magento\Framework\Mail\Template\TransportBuilder $transportBuilder,
    \Magento\Framework\Translate\Inline\StateInterface $inlineTranslation
){
    $this->_scopeConfig = $scopeConfig;
    $this->_transportBuilder = $transportBuilder;
    $this->inlineTranslation = $inlineTranslation;
}

public function execute(\Magento\Framework\Event\Observer $observer){

    $this->inlineTranslation->suspend();

    //return template id(custom_mail_template) setup in Configuration
    $emailtemplate = $this->_scopeConfig->getValue('custom_mail_template',\Magento\Store\Model\ScopeInterface::SCOPE_STORE);

    $transport = $this->_transportBuilder->setTemplateIdentifier($emailtemplate)->setTemplateOptions(
                                [
                                    'area' => \Magento\Framework\App\Area::AREA_FRONTEND,
                                    'store' => $this->_storeManager->getStore()->getId(),
                                ]
                            )->setTemplateVars(
                                    [
                                        'store' => $this->_storeManager->getStore(),
                                        'store URL' => $prodUrl
                                    ]
                                )->setFrom(
                                    [
                                        'email' => 'dotnet@gmail.com',
                                        'name' => 'Store Owner'
                                    ]
                                )->addTo(
                                    'training@gmail.com',
                                    'Training'
                                )->getTransport();

    $transport->sendMessage();
    $this->inlineTranslation->resume();
}

And rename: Helloworld/Custom/etc/email_template.xml to Helloworld/Custom/etc/email_templates.xml

I hope it help you.