Cluster->Create creates a new cluster.
Cluster
The 
Cluster entry provides a name for the cluster object. 
This is optional: when empty (or filled with separator characters, 
as space, tab, newline), the cluster will be named Cluster.
Object identification is explained in 
Introduction Identification.
A cluster is a container whose primary purpose is to contain other objects.
When a cluster is created, it has no child objects and consequently no visual
representation. The only way to select an empty cluster is therefore to write
its identification or to use the mechanisms provided by 
Cluster Select.
To avoid this problem, when 
Ok is pressed and the new cluster is created, 
the 
Cluster Create dialog is automatically replaced by the 
Cluster Link 
dialog, with the new cluster identification already inscribed on it. How to link 
objects to a cluster (TODO) is described in the section 
Cluster Link.