Yes, sorry about this. The type is called Properties. Actually, I created a test workfow with example (attached).
You can take a look to see how to create a Properties object and transfer and object of type Properties.
Also, from the log, you can see that in the first two scriptable tasks the id of the Properties object is the same. After user interaction (workflow passivated), the id of the Properties object is different (meaning a new instance was created and the state was populated from the db) but still the data entered in the frist two elements before the user interaction is still available.
Copy and paste from the workflow of how to create a property in case it is easier:
outprop = new Properties();
outprop.put("key1", "value1");
outprop.put("key2", {prop1: "valueProp1", prop2: "ValueProp2", prop3: {nested: "something"}, prop4: ["arr1", "arr2"]});