Add the following additional row to the message list in the issue.item.html (inside the 'tal:block tal:repeat="msg context/messages/reverse"'):
<tr><td colspan="4">
<table class="files" tal:condition="msg/files">
<tr>
<th i18n:translate="">File name</th>
<th i18n:translate="">Type</th>
<th i18n:translate="">Edit</th>
</tr>
<tr tal:repeat="file msg/files">
<td>
<a tal:attributes="href file/download_url"
tal:content="file/name">dld link</a>
</td>
<td tal:content="file/type" />
<td><a tal:condition="file/is_edit_ok"
tal:attributes="href string:file${file/id}">edit</a>
</td>
</tr>
</table>
</td></tr>