Of course, since UXP is a frame into which scriptable controls can be put, we can use the same code to put scriptable controls inside the view element of the frame (so you can have html view or XML defined UI inside the view, or multiple 'panes' in the view, some scriptable XML defined UI controls, some html, depending on what you want to do). Further, the scriptable controls can be put into the html as behaviours (e.g. so toolbars can be put above editable html).