title: Is it possible to declare global variables in Node-RED and use them on the node configuration?
body: <p>Supposing that I'm receiving information from many devices with the MQTT protocol and the following diagram is a simplified version of the block of one device:</p>
  
  <p><img src="https://i.stack.imgur.com/m5VrQ.png" alt="device one"></p>
  
  <p>So let's also suppose that all other devices have exactly the same diagram, except for the topic name that is going to change to <code>device2</code> for the second device, <code>device3</code> for the third device and so on, as follows:</p>
  
  <p><img src="https://i.stack.imgur.com/h2vFo.png" alt="device two"></p>
  
  <p>The problem is that I want a way of changing names inside the node's configuration without having to do it one by one. Like declaring a global variable that can be used not just in the function but in the nodes themselves. For example, the last picture could use something like: <code>MYVARIABLE_temperatureA</code> and <code>MYVARIABLE_temperatureB</code> as topics.</p>
  
  <p>So, is it possible to do something like this using the Node-RED? Or the solution lies just in creating a customized node that has a specific field for placing values?</p>