Add objects to the layer or move the layer to another window.
Hierarchy
Layers can be linked to objects above or below, in the Gamgi 
hierarchy. Pressing the button 
Below (the default), the 
Objects menu shows the classes of objects that can be owned 
by layers: Assembliy, Light, Cell, Cluster, Molecule, Group, Plane, 
Direction, Atom (the default), Orbital and Text. Pressing the button 
Above, the same menu shows the only class of objects that 
can own layers: Window.
Object
Gamgi expects users to identify first the layer or list of layers
and then the object to link. When the 
Layer entry is active
and empty, pressing the mouse over the graphic area in the current
window (local selection) creates a menu with all the layers in the 
window, which can then be selected. Initially, the identification 
of the current layer is entered in the 
Layer entry.
Gamgi is now expecting users to click on a object of the class 
currently selected in the 
Object menu. This object can be 
in a different layer or even in a different window (global selection). 
To select a visible object in a different layer, in the same window,
just press the mouse over the object, as if it was in the current
layer. To select objects without visual representation, as windows
and lights, press the mouse over the graphic area in a window,
to create a menu with all the objects of that class in the window 
(when the class is Light) or in Gamgi (when the class is Window), 
which can then be selected. To select an object in a different 
window, with the mouse, use exactly the same procedure, in that window.
Link
Gamgi suppports only one type of linking mode for Layer: 
Object.
The 
Object method links a layer to a single 
Object. 
When the 
Hierarchy is 
Above, the layer is unlinked 
from its previous window and linked to the new window. The layer 
history kept by the 
Undo and 
Save mechanisms is 
preserved in this operation. When the 
Hierarchy is 
Below, 
the object is unlinked from its current parent and linked to the layer. 
An error is issued when the parent already owned the child object. 
After the linking operation, Gamgi always puts on top
the window and layer containing the linked objects.