<$edit-text tiddler="$:/temp/captionbytag" tag="input" default=""/>

<table>
  <tr>
    <th>Tiddler</th>
    <th>Caption</th>
  </tr>
  <$list filter="[tag{$:/temp/captionbytag}]">
  <tr>
    <td>{{!!title}}</td>
    <td>{{!!caption}}</td>
  </tr>
  </$list>
</table>