The level of this clause_atom in the enclosing hierarchy.
This feature is present on objects of type clause_atom.
The original definition says: "The number of tab stops in the hierarchical display of the tree of clause atoms." How can this feature be understood without reference to a display? It seems to be the nesting depth of the clause atom, but in what tree?
Maybe we need a separate page about the clause_atoms and the structures they are a member of.
See also the values of this feature.