document(..., Subnodes => ...) -- a menu of documentation nodes

This option inserts into a documentation page a menu of subnodes. Here is a generic example:

Subnodes => {
          "An example of subnodes",
          TO "a link name",
          TO "another link name"
          },

The Subnodes option defines how the tree structure of the documentation is constructed. This is relevant when printing the documentation.