What version of vRO are you running? Are you using the web or the Java UI?
In the Java client you can force a specific selection by combining the 'Predefined answers' and 'Default value' properties for the field. Both can be bound to a vRO action if you have a more dynamic setting.
By the way, the tree view is available in the web UI starting from vRO 8.1
That is fantastic news about 8.1! I will test the migration upgrade in my LAB when I have a chance.
Thanks for your help! I converted the composite arrays to simple arrays to be listed in drop-down box using "Predefined answers" with an additional action, which I can then lookup the selected value by using yet another (hidden) input field that runs yet another action. I found this great method of reading in composite Harry objects and displaying the fields and values: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Working_with_Objects