Note that when panes are tabbed, dragging the title bar moves all of the tabbed panes at once.
You can "tear" a tab away by dragging it away from the others. You can also reorder the tabs by dragging them left and right.
Tip: When you're dragging panes, it's the position of the mouse cursor that determines how the pane's outline snaps into place. For example, to dock a pane below another one, drag the pane so the cursor is near the bottom edge of that pane. To "tab" one pane with another, drag the pane so the cursor is on top of the other pane's title bar.