proper session chapter;
cannot access session: refers to ROOT entry;

--- a/src/Tools/jEdit/src/isabelle_session.scala	Thu May 09 14:22:25 2019 +0200
+++ b/src/Tools/jEdit/src/isabelle_session.scala	Thu May 09 14:50:56 2019 +0200
@@ -88,8 +88,12 @@
         case Some(snapshot) =>
           val sessions = sessions_structure()
           val session = PIDE.resources.session_base.theory_qualifier(snapshot.node_name)
-          val chapter = sessions.get(session).getOrElse(Sessions.UNSORTED)
-          chapter + "/" + session
+          val chapter =
+            sessions.get(session) match {
+              case Some(info) => info.chapter
+              case None => Sessions.UNSORTED
+            }
+          chapter
       }
     VFSBrowser.browseDirectory(view, vfs_prefix + path)
   }