The cross-shaped arrangement of buttons in the middle of the manager's menus represents and controls a hierarchy of objects. All objects are associated with a node in a (partly seen) binary tree. Each button belongs to a node of the object hierarchy, in particular the middle button shows the current position in the tree. Clicking this button supplies some information about the present object, which information it provides is dependant of its class. Clicking one of the neighbouring buttons changes the current position. The button on the left side is the next upper object where you come from, the direction to the tree's root, buttons above and below the current object represent associated objects at the same level. The buttons on the right side are sub-objects. The buttons only a local view of the data hierarchy tree, all displayed objects are direct neighbours of the middle one, especially the buttons in the corners are not neighbour's neighbours, so don't be harmed if objects seem to disappear.
When walking through the tree, you will also see the graphics window change its contents, because it displays the current object (and the objects below). This is done by sending the current display method to the current object. Scenes automatically send the method not only to its object, but also to the subscene. A scene is also capable of sending a different (own) display method to its object and/or changed graphic properties, e.g. grid/patch switching or object transformations, locally for its object. Using this mechanism and different scenes with the same object (see further below) one object can be drawn using different display method at the same time, e.g. isolines and grid of a finite element solution.
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