Change the docking order
Changing the docking order of child objects in a DockPanel object will change their positions in the DockPanel object.
To change the docking order of objects in a DockPanel object
Click a DockPanel object to make it the active object.
In the Objects and Timeline panel, click a child object of the DockPanel object to select it.
Drag and drop the child object 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 object, either on the artboard or in the Objects and Timeline panel, and selecting one of the options under Order.