Subdialogs are opened when clicking on a preview (like WYSIWYG) or on a special button (like Hyperlink).

1. The sub-dialog uses up as much height as is possible, as it usually needs the space
2. Click on "back" leaves the dialog and returns to the list.
3. This also works when the data is still incomplete - so validation checks don't prevent leaving the sub-dialog
4. Pressing Esc behaves the same way
5. Click on the background behaves the same way.
6. Mouse-Up on the background has no effect (so selecting text and overdragging doesn't close the dialog)
7. File-drop on the background has no effect