dev/defs/custom_property_string.json

{
  "name": "CustomPropertyString",
  "key": {
    "int": 130,
    "string": "custompropertystring"
  },
  "extends": "custom_property.json",
  "properties": {
    "propertyValue": {
      "type": "String",
      "initialValue": "''",
      "animates": true,
      "key": {
        "int": 246,
        "string": "value"
      }
    }
  }
}