Ok, gotcha. You confused me with the notepad++ screenshot. I thought you were trying to build a new one or something.
To answer your question from before, those highlighted snippets are placeholders for variables and blocks. I won’t pretend that I know the exact details, because I don’t.
So, normally the default Templates are called from these two locations. Perhaps there is something wrong with these files?:
vendor/magento/module-sales/view/frontend/email/shipment_new.html
vendor/magento/module-sales/view/frontend/email/shipment_new_guest.html
In case you need them, the templates are below if you want to create a new template in the backend to replace the broken ones.
New Shipment
New Shipment - Subject
{{trans "Your %store_name order has shipped" store_name=$store.getFrontendName()}}
New Shipment - Template Content
{{template config_path="design/email/header_template"}}
<table>
<tr class="email-intro">
<td>
<p class="greeting">{{trans "%name," name=$order.getCustomerName()}}</p>
<p>
{{trans "Thank you for your order from %store_name." store_name=$store.getFrontendName()}}
{{trans 'You can check the status of your order by <a href="%account_url">logging into your account</a>.' account_url=$this.getUrl($store,'customer/account/',[_nosid:1]) |raw}}
{{trans 'If you have questions about your order, you can email us at <a href="mailto:%store_email">%store_email</a>' store_email=$store_email |raw}}{{depend store_phone}} {{trans 'or call us at <a href="tel:%store_phone">%store_phone</a>' store_phone=$store_phone |raw}}{{/depend}}.
{{depend store_hours}}
{{trans 'Our hours are <span class="no-link">%store_hours</span>.' store_hours=$store_hours |raw}}
{{/depend}}
</p>
</td>
</tr>
<tr class="email-summary">
<td>
<p>{{trans "Your shipping confirmation is below. Thank you again for your business."}}</p>
<h1>{{trans "Your Shipment #%shipment_id for Order #%order_id" shipment_id=$shipment.increment_id order_id=$order.increment_id}}</h1>
</td>
</tr>
<tr class="email-information">
<td>
{{depend comment}}
<table class="message-info">
<tr>
<td>
{{var comment|escape|nl2br}}
</td>
</tr>
</table>
{{/depend}}
{{block class='Magento\\Framework\\View\\Element\\Template' area='frontend' template='Magento_Sales::email/shipment/track.phtml' shipment=$shipment order=$order}}
<table class="order-details">
<tr>
<td class="address-details">
<h3>{{trans "Billing Info"}}</h3>
<p>{{var formattedBillingAddress|raw}}</p>
</td>
{{depend order.getIsNotVirtual()}}
<td class="address-details">
<h3>{{trans "Shipping Info"}}</h3>
<p>{{var formattedShippingAddress|raw}}</p>
</td>
{{/depend}}
</tr>
<tr>
<td class="method-info">
<h3>{{trans "Payment Method"}}</h3>
{{var payment_html|raw}}
</td>
{{depend order.getIsNotVirtual()}}
<td class="method-info">
<h3>{{trans "Shipping Method"}}</h3>
<p>{{var order.getShippingDescription()}}</p>
</td>
{{/depend}}
</tr>
</table>
{{layout handle="sales_email_order_shipment_items" shipment=$shipment order=$order}}
</td>
</tr>
</table>
{{template config_path="design/email/footer_template"}}
New Shipment (Guest)
New Shipment (Guest) - Subject
{{trans "Your %store_name order has shipped" store_name=$store.getFrontendName()}}
New Shipment (Guest) - Template Content
{{template config_path="design/email/header_template"}}
<table>
<tr class="email-intro">
<td>
<p class="greeting">{{trans "%name," name=$billing.getName()}}</p>
<p>
{{trans "Thank you for your order from %store_name." store_name=$store.getFrontendName()}}
{{trans 'If you have questions about your order, you can email us at <a href="mailto:%store_email">%store_email</a>' store_email=$store_email |raw}}{{depend store_phone}} {{trans 'or call us at <a href="tel:%store_phone">%store_phone</a>' store_phone=$store_phone |raw}}{{/depend}}.
{{depend store_hours}}
{{trans 'Our hours are <span class="no-link">%store_hours</span>.' store_hours=$store_hours |raw}}
{{/depend}}
</p>
</td>
</tr>
<tr class="email-summary">
<td>
<p>{{trans "Your shipping confirmation is below. Thank you again for your business."}}</p>
<h1>{{trans "Your Shipment #%shipment_id for Order #%order_id" shipment_id=$shipment.increment_id order_id=$order.increment_id}}</h1>
</td>
</tr>
<tr class="email-information">
<td>
{{depend comment}}
<table class="message-info">
<tr>
<td>
{{var comment|escape|nl2br}}
</td>
</tr>
</table>
{{/depend}}
{{block class='Magento\\Framework\\View\\Element\\Template' area='frontend' template='Magento_Sales::email/shipment/track.phtml' shipment=$shipment order=$order}}
<table class="order-details">
<tr>
<td class="address-details">
<h3>{{trans "Billing Info"}}</h3>
<p>{{var formattedBillingAddress|raw}}</p>
</td>
{{depend order.getIsNotVirtual()}}
<td class="address-details">
<h3>{{trans "Shipping Info"}}</h3>
<p>{{var formattedShippingAddress|raw}}</p>
</td>
{{/depend}}
</tr>
<tr>
<td class="method-info">
<h3>{{trans "Payment Method"}}</h3>
{{var payment_html|raw}}
</td>
{{depend order.getIsNotVirtual()}}
<td class="method-info">
<h3>{{trans "Shipping Method"}}</h3>
<p>{{var order.getShippingDescription()}}</p>
</td>
{{/depend}}
</tr>
</table>
{{layout handle="sales_email_order_shipment_items" shipment=$shipment order=$order}}
</td>
</tr>
</table>
{{template config_path="design/email/footer_template"}}
