koobas.hobune.stream
UIToolkit / UI Builder How do I add elements to a Foldout?
How can I add an element to a foldout via code of UI builder? 
The form above I made with the UI Builder window. I can get buttons and toggle elements fine through code.
I'm trying to implement foldout (dd_heading) but cannot for the life of me figure out how to add elements to the foldout. I've looked at the documentation but I can't seem to grasp how I add elements to a foldout.
I can see the child elements in the foldout but don't know how I can access them. 
The form is a text editor which can edit Heading text and Body text. User selects the dropdown to switch between Heading & Body.
