nodered_cfg/node_modules/node-red-dashboard/nodes/locales/en-US/ui_dropdown.html

<script type="text/html" data-help-name="ui_dropdown">
    <p>Adds a dropdown select box to the user interface.</p>
    <p>Multiple value / label pairs can be added as required. If the label is not specified the
    value will be used for both.</p>
    <p>The configured value of the selected item will be returned as <code>msg.payload</code>.</p>
    <p>Setting <code>msg.payload</code> to one of the item values will preset the choice in the dropdown.
    If using the multi-select option then the payload should be an array of values.</p>
    <p>Optionally the <b>Topic</b> field can be used to set the <code>msg.topic</code> property.</p>
    <p>The Options may be configured by inputting <code>msg.options</code> containing an array.
    If just text then the value will be the same as the label, otherwise you can specify both by
    using an object of <code>"label":"value"</code> pairs :</p>
    <code>[ "Choice 1", "Choice 2", {"Choice 3":"3"} ]</code>
    <p></p>
    <p>If the "Allow multiple selections" output option is enabled - the result will be returned as an array instead of a string.</p>
    <p>If a <b>Class</b> is specified, it will be added to the parent card. This way you can style the card and the elements inside it with custom CSS. The Class can be set at runtime by setting a <code>msg.className</code> string property.</p>
</script>