Edit 
				
					{
   "blockOptions": {
      "method": {
         "args": {
            "deviceGroup": "deviceGroup",
            "itemGroup": "itemGroup",
            "value": "value"
         },
         "name": "groupSetItemValue"
      }
   },
   "blockType": "then",
   "fields": [
      {
         "name": "deviceGroup",
         "type": "device_group",
         "value": "device_group_id"
      },
      {
         "name": "itemGroup",
         "type": "item_group",
         "value": "item_group_id"
      },
      {
         "name": "value",
         "type": "int",
         "value": 10
      }
   ]
}
Edit

Examples of possible values:

				
					{
    "name":"value",
    "type":"bool",
    "value": false
}				
			
				
					{
    "name":"value",
    "type":"token",
    "value": "idle_off"
}				
			
				
					{
    "name":"value",
    "type":"power",
    "value": 30,
    "scale": "watt"
}				
			
				
					{
    "name":"value",
    "type": "float",
    "value": 5.0
}				
			
				
					{
    "name":"value",
    "type": "string",
    "value": "example"
}

Note: Available since advanced_scenes/1.63.