This Desk.com custom email widget theme adds an example custom field and article suggest functionality. To input this code into your widget, login to your Desk.com Admin panel and go to Channels -> Email -> Widgets. Be sure to update the "ajax" part of the JavaScript code to point to your Desk.com subdomain (instead of YOUR-SITE).

1 - Header.html

<title>{{ site.company_name }}</title>

<link rel="icon" type="image/vnd.microsoft.icon" href='{{ "/favicon.png" | portal_image_url: image_asset_host }}' />

<link rel="icon" type="image/png" href='{{ "/favicon.png" | portal_image_url: image_asset_host }}' />

<style type="text/css">

.customer_inner_widget

{

padding-top:0px;

padding-bottom:20px;

padding-right:20px;

padding-left:20px;

}
  
.article-links {
-webkit-box-sizing: border-box;
-moz-box-sizing: border-box;
box-sizing: border-box;
margin: 5px 0 15px 0;
width: 100%;
padding: 10px;
border: 1px dotted rgb(180, 180, 180);
}
  
.customer_widget {
  top: auto; 
  bottom: auto;
}
  
.widget_button_extra_email {
  margin: 15px 0 0 0;
  position: relative; 
  left: auto;
}
  
.widget_button_extra_email {
  margin: 15px 0 0 0;
  position: relative; 
  left: auto;
}

</style>

2 - Body.html

<div id="customer_widget_main" class="customer_widget">

<div class="inside_title" style="font-size:25px">{{site.company_name}} {{system.snippets.help_center}}</div>

<div class="inside_desc">{{system.snippets.email_support}} </div>

<div class="customer_inner_widget" >

{% if current_user == nil or current_user.is_guest %}
<div class="input" ><span class="form_label">{{system.snippets.your_name}}:</span>

{{ interaction_name }}

</div>

<div class="input" ><span class="form_label">{{system.snippets.your_email}}:</span>

{{ interaction_email }}

</div>
{% endif %}

<div class="input"><span class="form_label">{{system.snippets.subject}}:</span>

{{ email_subject }}

</div>
  
<div class="input"><span class="form_label">Brand:</span>
  <input class="default l" type="text" name="ticket[custom_brand]" id="ticket_custom_brand" value="" />
</div>

<div class="input"><span class="form_label">{{system.snippets.message}}:</span>

{{ email_body }}

</div>
  
  
  
  
  
  
<div id="autosuggest" class="article-links" style="display: none;"></div>
<div id="common" class="article-links">
  <h4>Common Questions</h4>
  <ul class="no-bullets">
    <li><span class="label label-info">New</span> <a class="article" href=
    "/customer/portal/articles/566428-getting-started-multilingual-support">Multilingual
    Support</a></li>

    <li><a class="article" target="_blank" href=
    "/customer/portal/articles/351939-how-do-i-access-the-desk-com-mobile-app-">Accessing
    Desk.com Mobile</a></li>

    <li><a class="article" target="_blank" href=
    "/customer/portal/articles/2619-custom-fields-for-case-and-customer">Adding
    and Using Custom Fields</a></li>

    <li><a class="article" target="_blank" href=
    "/customer/portal/articles/1835-how-do-i-add-an-email-form-to-my-website-">Adding
    an Email/Contact Form</a></li>

    <li><a class="article" target="_blank" href=
    "/customer/portal/articles/1548-how-to-use-your-own-domain-for-the-portal">Change
    the Address of your Portal</a></li>

    <li><a class="article" target="_blank" href=
    "/customer/portal/articles/749107-integrating-desk-com-and-salesforce">Integrate
    Salesforce and Desk.com</a></li>

    <li><a class="article" target="_blank" href=
    "/customer/portal/articles/1376-understanding-business-rules">Understanding
    Business Rules</a></li>

    <li><a class="article" target="_blank" href="/customer/portal/articles/63009">Send Notifications For
    Cases</a></li>

    <li><a class="article" target="_blank" href=
    "/customer/portal/articles/2741-understanding-case-filters">Understanding
    Case Filters</a></li>

    <li><a class="article" target="_blank" href=
    "/customer/portal/articles/3085-how-do-i-add-a-chat-form-to-my-site-">Adding
    Chat to your Site</a></li>

    <li><a class="article" target="_blank" href=
    "/customer/portal/articles/1424-understanding-the-case-lifecycle">Understanding
    Case Statuses</a></li>

    <li><a class="article" target="_blank" href="/customer/portal/articles/305053-glossary-of-terms">Glossary
    of Terms</a></li>
  </ul>
</div>
  
  
  
  
  
  

<div class='input'><span class='form_label'>{{system.snippets.file_attachment}}:</span>

{{ file_attachment }}

</div>

{{hidden_parameters }}

{{ submit_button }}

{{ interaction_info }}

</div><!--customer_inner_widget-->

</div><!--customer_widget_main-->

<script>
$(function() {
  
// Real-time auto-suggest
  $('#email_subject, #email_body').keyup(function() {
    count = 0;
    if ($('#email_subject').val().length > 2 || $('#email_body').val().length > 2) {
      query = $('#email_subject').val() + " " + $('#email_body').val();
      $.ajax({
        url: 'https://YOUR-SITE.desk.com/customer/portal/articles/autocomplete?term=' + query,
        dataType: 'json'
      }).done(apiSuccess).fail(apiFail);
    } else { 
      $("#autosuggest").hide();
      $("#common").show();
    }
  });
  
});

apiSuccess = function(data) {
  auto_suggest_content = "";
  auto_suggest_articles = "";
  auto_suggest_questions = "";
  $('#autosuggest').html("<h4>Do these help?</h4><ul class='no-bullets'></ul>");
  $.each(data, function() {
    var html = $(this.label);
    article_title = html.find(".article-autocomplete-subject").html();
    if (this.id.indexOf("questions") !== -1) {
      auto_suggest_questions += '<li><a target="_blank" href="' + this.id + '" class="discussion">' + article_title + '</a></li>';
    } else {
      auto_suggest_articles += '<li><a target="_blank" href="' + this.id + '" class="article">' + article_title + '</a></li>';
    }
    count++;
  });
  if (count > 0) {
    $('#autosuggest ul').append(auto_suggest_articles + auto_suggest_questions);
    $("#common").hide();
    $("#autosuggest").show();
  } else {
    $("#autosuggest").hide();
    $("#common").show();
  }
};
  
apiFail = function(data) {
    
};
</script>