Change the docking order
Changing the docking order of child elements in a dock panel will change their positions in the dock panel.
Double-click a dock panel to make the dock panel the active element.
In the objects view under Objects and Timeline in the Interaction panel, click a child element of the dock panel to select it.
Drag and drop the child element to the desired position in the docking order. You are really just changing the order of the stack (z-order or markup order).
You can also change the docking order by right-clicking the child element, either on the artboard or under Objects and Timeline, and selecting one of the options under Order.