I did a very quick test on OS X.  Comments:

1. In keeping with Apple Human Interface Guidelines, the "Options" menu is different on OS X: the "Configure IDLE" menu item appears as a "Preferences" menu item in the "IDLE" application menu row.  So, as it stands, adding the "Configure Extensions" menu item doesn't work on OS X due to the menu tailoring.  This addition makes it work:

diff --git a/Lib/idlelib/macosxSupport.py b/Lib/idlelib/macosxSupport.py
--- a/Lib/idlelib/macosxSupport.py
+++ b/Lib/idlelib/macosxSupport.py
@@ -141,9 +141,9 @@
     # menu
     del Bindings.menudefs[-1][1][0:2]

-    # Remove the 'Configure' entry from the options menu, it is in the
+    # Remove the 'Configure IDLE' entry from the options menu, it is in the
     # application menu as 'Preferences'
-    del Bindings.menudefs[-2][1][0:2]
+    del Bindings.menudefs[-2][1][0]

     menubar = Menu(root)
     root.configure(menu=menubar)

2. The buttons on the Extensions Configuration aren't wide enough for the default Cocoa Tk 8.5 text on them (Ok, Apply, Cancel) so they overflow to two lines.  In contrast, the similar buttons on the IDLE Preferences window display correctly.

3. On the ParenMatch configuration tab, there is a text box for "style" (with the default value of "expression").  There is no clue to what this means or what values are valid.  Could this be some other widget if there is a known set of value?

4. If the enabled setting for CallTips are changed while edit windows are open, the existing windows are not affected.  New edit windows do observe the new setting.  (I didn't try this with other extensions.)

5. The appearance of the boolean options on the extensions panels vary among the various Tk's supported on OS X and none of the result are totally satisfactory; see the images in the zipfile upload.  I think the main problem is that the widgets are centered in the frame.  For Cocoa Tk, this results in a check box towards the left and the label centered in the remaining space.  For the other two (Carbon 8.4 and X11, it results in a very wide toggle button.


It would probably be a good idea for someone who uses IDLE to do a more thorough review of all of the options on all of the Tk variants we support (e.g. Windows, Linux X11, OS X Cocoa, OS X Carbon, OS X X11).  As this quick look shows, there are almost always differences (subtle and not so subtle) among them.