This is the second tab option in the "Edit Space" window.
This gives you the option of creating separate spaces from the composite space. So if you have used the Divide Space tool you must use the Separate Composite space tool to make the Spaces complete separate entities. The other scenario where this tab would be utilised is when you have connected two (or more) spaces and wish them to be separated again.
Edit Vertices
This is the third tab option in the "Edit Space" window.
You selects vertices, which are highlighted in the view. Multiple selections can be made by using the <CTRL> key. When the "Move Vertices" button is pressed the defined shift in x, y and z is applied.
When your are in a 2D view the button becomes active, which allows you to drag the selected vertices in the graphics window.
If after making the defined modifications to the space, a surface is warped, then the following pop-up warning is issued and you can either resume editing the vertices or restore the original space.
button becomes active, which allows you to drag the selected vertices in the graphics window. 