You can select encapsulated nodes by selecting them in the scene panel, Outliner, or Hypergraph. In the Hypergraph Connections editor, encapsulated nodes will be hidden in their respective containers until you expand the container (see Expand and collapse containers).
From the Hypergraph Connections editor, you can select all the nodes in a container at once.
To select all the nodes in a container
 the
            container whose contents you want to select and choose Select
               Container Contents.
  the
            container whose contents you want to select and choose Select
               Container Contents.
            
         In either case, if the container is in Black Box mode, only published nodes are selected.