tuned, following hints by IntelliJ IDEA;

--- a/src/Tools/jEdit/src/main_plugin.scala	Thu Aug 04 12:00:58 2022 +0200
+++ b/src/Tools/jEdit/src/main_plugin.scala	Thu Aug 04 12:14:56 2022 +0200
@@ -242,7 +242,7 @@
             val model = Document_Model.init(session, node_name, buffer)
             for {
               text_area <- JEdit_Lib.jedit_text_areas(buffer)
-              if Document_View.get(text_area).map(_.model) != Some(model)
+              if !Document_View.get(text_area).map(_.model).contains(model)
             } Document_View.init(model, text_area)
           }
         }
@@ -298,7 +298,7 @@
 
     if (startup_failure.isDefined && !startup_notified) {
       message match {
-        case msg: EditorStarted =>
+        case _: EditorStarted =>
           GUI.error_dialog(null, "Isabelle plugin startup failure",
             GUI.scrollable_text(Exn.message(startup_failure.get)),
             "Prover IDE inactive!")
@@ -309,7 +309,7 @@
 
     if (startup_failure.isEmpty) {
       message match {
-        case msg: EditorStarted =>
+        case _: EditorStarted =>
           if (resources.session_errors.nonEmpty) {
             GUI.warning_dialog(jEdit.getActiveView,
               "Bad session structure: may cause problems with theory imports",
@@ -369,7 +369,7 @@
               Completion_Popup.Text_Area.exit(text_area)
           }
 
-        case msg: PropertiesChanged =>
+        case _: PropertiesChanged =>
           for {
             view <- JEdit_Lib.jedit_views()
             edit_pane <- JEdit_Lib.jedit_edit_panes(view)