Simple form with just 2 columns, a dropdown and textarea, and the rule to show textarea when a user made a choice in a dropdown and that is greater than 2 


On the screenshot below you can see how the Registrations Control macro looks like in the editor

And the form dialog itself, online demo


All the customizations, to change the border widths and to make them invisible on the table which renders fields in 2 column mode have been done using the Confluence source editor, adding CSS styles


Storage format for this simple 2 column form

<ac:structured-macro ac:macro-id="a27cf138-2081-4b5c-8dcf-435b5a4c82e5" ac:name="confiform" ac:schema-version="1">
  <ac:parameter ac:name="formName">f1</ac:parameter>
  <ac:rich-text-body>
    <p>
      <ac:structured-macro ac:macro-id="4bd4edbc-4d04-47ed-823a-e90521ec741a" ac:name="confiform-field-definition" ac:schema-version="1">
        <ac:parameter ac:name="fieldName">choice</ac:parameter>
        <ac:parameter ac:name="fieldLabel">Choice</ac:parameter>
        <ac:parameter ac:name="values">false[1=One|2=Two|3=Three|4=Four|5=Five|]</ac:parameter>
        <ac:parameter ac:name="fieldDescription">When more than 2 selected the comment field is shown</ac:parameter>
        <ac:parameter ac:name="type">select</ac:parameter>
      </ac:structured-macro>
    </p>
    <p>
      <ac:structured-macro ac:macro-id="3af9129a-882b-4ba9-8f35-ce8af165c06d" ac:name="confiform-field-definition" ac:schema-version="1">
        <ac:parameter ac:name="fieldName">comment</ac:parameter>
        <ac:parameter ac:name="fieldLabel">Type your comment</ac:parameter>
        <ac:parameter ac:name="type">textarea</ac:parameter>
      </ac:structured-macro>
    </p>
    <p>
      <ac:structured-macro ac:macro-id="b91cda0e-59b2-4bb6-a7db-b319ed648d15" ac:name="confiform-field-definition-rules" ac:schema-version="1">
        <ac:parameter ac:name="condition">choice:&gt;2</ac:parameter>
        <ac:parameter ac:name="fieldName">comment</ac:parameter>
        <ac:parameter ac:name="action">Show field</ac:parameter>
        <ac:parameter ac:name="actionFieldName">choice</ac:parameter>
        <ac:parameter ac:name="withReverseRule">true</ac:parameter>
      </ac:structured-macro>
    </p>
  </ac:rich-text-body>
</ac:structured-macro>
<ac:structured-macro ac:macro-id="67eb0856-9621-4e39-84b2-051e67ec0a3d" ac:name="confiform-entry-register" ac:schema-version="1">
  <ac:rich-text-body>
    <table border="0" style="border: 0.0px;">
      <tbody style="width: 100.0%;">
        <tr style="border: 0.0px;">
          <td style="border: 0.0px;">
            <ac:structured-macro ac:macro-id="683053d6-c2ba-4fdd-b2d6-9db427fb5421" ac:name="confiform-field" ac:schema-version="1">
              <ac:parameter ac:name="fieldName">choice</ac:parameter>
              <ac:parameter ac:name="withLabel">true</ac:parameter>
            </ac:structured-macro>
          </td>
          <td style="border: 0.0px;width: 70.0%;">
            <ac:structured-macro ac:macro-id="1a7b606b-d028-4aa2-997d-b9f82a168536" ac:name="confiform-field" ac:schema-version="1">
              <ac:parameter ac:name="fieldName">comment</ac:parameter>
              <ac:parameter ac:name="withLabel">true</ac:parameter>
            </ac:structured-macro>
          </td>
        </tr>
      </tbody>
    </table>
  </ac:rich-text-body>
</ac:structured-macro>