Node-RED block in Snap4City Microservice library node-red-contrib-snap4city-user is "synoptic-subscribe">
    <p>Shows an output message when the value of the Synoptic Variable chosen in configuration is modified inside a dashboard, with a widget made in svg.</p>

    <h3>Outputs</h3>
    <dl class="message-properties">
        <dd> Synoptic Variable value that has been observed</dd>
    </dl>