You can change the Layout of the tabs by dragging them to other panels. Anywhere you can drop the tab will change the red x into a green checkmark.
Anchor tab to the selected tab. This means you will switch between the original tab and the added tab in the same space, and can only view one of them at a time in a larger window.
Splits the space the selected tab occupies. When neighbouring tabs are resized, the split tabs will maintain their proportions.
Docks tab on the edge of the selected tab. Docked tabs will not move when other tabs are resized.
Pins tab to the edge of the screen. Clicking on the tab opens it up, and clicking it again or clicking anywhere else hides it again.
Docks tab to the edge of the screen.