Showing variable on GUI

---

From P4co86

Here’s an example of a basic variables device that you can add to your GUI to visualize its value :

{
      "id": "control-variable",
      "name": "test var",
      "class": "VariablesDevice",
      "variables": [
        {
          "name": "myVar",
          "expression": "$value",
          "type": "number"
        }
      ]
    },