This method can be used to add a new page to a register group. The new page specified
by "obj" must be a detached group object. This detached group object will then
be added as the register's last page. After this method returns the specified group
object will change its state from detached to attached. That is why you must no
longer use functions that expect a detached object with this object now.
Detached MUI objects can be created either by calling the mui.CreateObject()
function or by explicitly detaching them from their parent by using the
Register.ClosePage method.
This feature requires at least MUI 4.0.