Hello,
You would be correct in assuming that you will need to set the Zorder for everything on your Designer tab that overlaps. Hierarchy does not necessarily determine what shows as on top. As for rearranging widgets in the hierarchy, you will need to click and drag them. When dropped on a widget that can hold it as a child widget the widget will then be placed under it. You can also reorder the widget by clicking and dragging them upward in the hierarchy.