The tab pane, or individual tabs can be docked against any of the Editor's edges. When you drag a tab over one of the docking icons a shaded rectangle identifies where the tab will docked.
Any changes you make to the tab locations will be remembered by the Editor, and will be displayed in the same location when you open the Editor again. You can use the Reset Panels option on the Editor's View tab to return all of the tabs to their original location.