app/bundles/NotificationBundle/Resources/views/Notification/preview.html.twig

{#
  Variables
    - notification (\Mautic\NotificationBundle\Entity\Notification)
#}
<label>Preview</label>
<div id="notification-preview" class="panel panel-default">
    <div class="panel-body">
        <div class="row">
            <div class="icon height-auto text-center">
                <span class="ri-notification-3-fill fs-48"></span>
            </div>
            <div class="text height-auto">
                <h4>
                    {%- if notification.heading -%}
                        {{- notification.heading -}}
                    {%- else -%}
                        Your notification header
                    {%- endif -%}
                </h4>
                <p>
                    {%- if notification.message %}
                        {{- notification.message -}}
                    {%- else -%}
                        The message body of your notification
                    {%- endif -%}
                </p>
                <span>{{ app.request.server.get('HTTP_HOST') }}</span>
            </div>
        </div>
        {% if notification.url and notification.button %}
            <hr>
            <a href="{{ notification.url }}">{{ notification.button }}</a>
        {% endif %}
    </div>
</div>