Hi, you probably moved on from this issue but incase it helps anyone else.
I used an invoke code acitivity and passed the jobject as an in/out argument.
The code I used to add a property to the end of the JObject was:
TestJobject.Add(new JProperty(“NewProperty”,“New Value”))
I adapted an example from this website if you want more info:
[https://www.newtonsoft.com/json/help/html/ModifyJson.htm](http://)