A form with ConfiForms Field Definition Rule to show and hide the section (div) on the page

 

<script>
function toggleSection(show) {
  if (show) {
    AJS.$('.mysection').show();
  } else {
	AJS.$('.mysection').hide();
  }
}
</script>

Screenshot from the Confluence editor

Storage format for the solution

<ac:structured-macro ac:macro-id="450f2bd8-54a0-4092-acb6-f24962478c6f" ac:name="confiform" ac:schema-version="1">
  <ac:parameter ac:name="formName">f1</ac:parameter>
  <ac:rich-text-body>
    <ac:structured-macro ac:macro-id="5ac062fc-45d4-43c3-b558-d4286911aeca" ac:name="confiform-entry-register" ac:schema-version="1">
      <ac:parameter ac:name="embedded">true</ac:parameter>
      <ac:rich-text-body>
        <p>
          <ac:structured-macro ac:macro-id="8e131578-8f87-43d6-b247-e434579cf3b0" ac:name="confiform-field" ac:schema-version="1">
            <ac:parameter ac:name="fieldName">toggle</ac:parameter>
            <ac:parameter ac:name="withLabel">true</ac:parameter>
          </ac:structured-macro>
        </p>
        <div class="confluence-information-macro confluence-information-macro-warning mysection" style="display: none;">
          <p class="title">Hello there</p>
          <span class="aui-icon aui-icon-small aui-iconfont-error confluence-information-macro-icon"> </span>
          <div class="confluence-information-macro-body">
            <p>Have fun with ConfiForms</p>
          </div>
        </div>
      </ac:rich-text-body>
    </ac:structured-macro>
    <p>
      <ac:structured-macro ac:macro-id="2b3465a3-a546-4e67-a164-4a0eeb562316" ac:name="confiform-field-definition" ac:schema-version="1">
        <ac:parameter ac:name="fieldName">toggle</ac:parameter>
        <ac:parameter ac:name="fieldLabel">Toggle me</ac:parameter>
        <ac:parameter ac:name="type">checkbox</ac:parameter>
      </ac:structured-macro>
    </p>
    <p>
      <ac:structured-macro ac:macro-id="cf0a3f2d-7789-45e6-b68a-ce5807760529" ac:name="confiform-field-definition-rules" ac:schema-version="1">
        <ac:parameter ac:name="values">toggleSection([entry.toggle]);</ac:parameter>
        <ac:parameter ac:name="action">Run custom JavaScript</ac:parameter>
        <ac:parameter ac:name="onUserActionOnly">true</ac:parameter>
        <ac:parameter ac:name="actionFieldName">toggle</ac:parameter>
      </ac:structured-macro>
    </p>
  </ac:rich-text-body>
</ac:structured-macro>
<ac:structured-macro ac:macro-id="9d95f2e0-7daa-4a1b-9b26-2988d48447e3" ac:name="html" ac:schema-version="1">
  <ac:plain-text-body><![CDATA[<script>
function toggleSection(show) {
  if (show) {
    AJS.$('.mysection').show();
  } else {
	AJS.$('.mysection').hide();
  }
}
</script>]]></ac:plain-text-body>
</ac:structured-macro>