Register.ClosePage -- remove page from register group (V1.2)
mui.DoMethod(id, "ClosePage", obj)
This method will close the page tab specified by "obj". The group object that
constitutes the page that is being closed will then change its state from attached
to detached. This means that you could attach it now to another register or group
using a function like Group.Insert and Register.AddPage, respectively,
or you could free it using mui.FreeObject().