Bring to Front, Send to Back
The "Bring to Front" (or Ctrl-J on the keyboard) and "Send to Back" (or Ctrl-K on the keyboard) functions change the depth order of overlapped objects of the same layer. These functions facilitate the selection and the manipulation of an object when it is located "under" another object.
In this example, the "Unit" counter is located under the green area. It cannot be selected with the mouse.
In the green area's contextual menu, select the Send to Back item which will move the area towards the inferior level, pushing up the "Unit" counter to an accessible level.
The "Unit" Counter now becomes accessible to be selected with the mouse :