Graph: pan with left or right, open with the other

Backend/Settings.py

@@ -49,9 +49,10 @@ DefaultSettings: dict[str, Any] = {
     # live preview). "Separate": rendered View and raw Edit are two modes.
     "MarkdownEditing": "Live",
     # Graph view: directories as dots too (off: only files and the references
-    # between them), and the mouse button that pans ("Left", "Middle", "Right").
+    # between them), and the mouse button that pans ("Left" or "Right"; the
+    # other one opens a dot).
     "GraphShowDirectories": True,
-    "GraphPanButton": "Middle",
+    "GraphPanButton": "Right",
 }
 
 DefaultThemesDirectory = ApplicationDirectory / "DefaultThemes"