Trying to access values from nodes to render in email template using swift mailer

I'm currently working on trying to build an email html template using swift mailer. My problem right now is how can I customize the template to fetch the values from the nodes and render them in the email template. Fetch and print/render the node values only from the nodes that will be sent as shown in the screenshot below.

Swift mailer has a default way to output the values from all the fields using

Is there a way I could access the values from the fields and render them on the template. Something like the code below that works on node template

or

Swift mailer has a way to render values via preprocess but I can't seem to make it work. Below is the code that is a work in progress

https://www.drupal.org/node/1590184

function swiftmailer_preprocess_swiftmailer(&$variables) {
    $variables['node_title'] = $node->getTitle();
}

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