The position of the Project Explorer (or any other) view in the Workbench window can be changed.
Click in the title bar of the Project Explorer view and drag the view across the Workbench window. Do not release the mouse button yet.
While still dragging the view around on the Workbench window, note that various drop outlines appear. These drop outlines indicate where the view will dock in relation to the view or editor area underneath the cursor when the mouse button is released.
Dock the Project Explorer in the stack with the Outline view and notice the results of this action. Note the drop outline next to the tab of the view you are dropping next to.
Click and drag the Project Explorer's title bar to re-dock the view as its own view stack on top of the Outline view. Note the drop outline showing the orientation of the views after the drop.
Click and drag the Project Explorer's title bar outside the Workbench window to make it a "detached" window (a view stack in its own window). Note the drop outline showing it will be outside the main workbench window.
Finally, drag the Project Explorer view over the editor area. A drop outline will be displayed to show the view orientation related to the editor area.
Rearranging views and editors
Rearranging tabbed views
Maximizing and minimizing