Display the graphics under the user specified <NameTree "graphic tree", instead of the usual <GREG tree. The tree is created if needed, cleared if it already exists.
Using different "graphic trees" allows the user to simultaneously display (the same or different) data in different ways, as each tree inherits a specific window.
A few names should not be used as NameTree: VSIDE, POPUP, CCT because they are already used by some specific plotting routine.