You can edit namespaces using the Namespace Editor. These operations include setting the current namespace and turning on Relative Namespaces mode so that you can refer to namespaces relative to the current namespace.
Set current namespace using the Namespace Editor
The icon indicates that the selected namespace is now the current namespace.
You can refer to namespaces relative to the current namespace. This can help streamline the Outliner and allows you to simplify MEL commands by eliminating the need to constantly include the namespace.
For example, if you had a cube in a namespace named cube_space and set the current namespaces to cube_space, you could use the command setAttr pCube1.translateX rather than having to specify setAttr cube_space:pCube1.translateX.
Use the Namespace Editor to turn on Relative Namespaces mode
Maya updates the display of all namespaces in the Outliner relative to the current namespace.