Pending review on non-Windows systems, I believe the attached patch patch is about ready to commit (after re-enabling all tests).  As for Ned's 5 points:

1. macosxSupport.py changes are incorporated.

2. Buttons should work with re-use of the ConfigDialog code.  I altered create-action-buttons to incorporate the padding above the buttons.

5. The boolean option buttons were stretched because of 'sticky=NSEW'.  Changing that to 'sticky=W' moves leaves them sized as specified and left-justified.  Removing 'sticky=W' leaves them centered, but I think I prefer them to the left.

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3. It is annoying that ConfigParser ignores comments when reading and deletes them (by not writing them) when saving changed options. Even if it were changed, that would not help Idle on current versions.

We could establish more option name conventions (as we already have for section names and 'enable..').  For instance, if we did not externally specify that 'enable' was bool, the file could have 'enable-type=bool'.  For parenmatch, 'style-vals=expression, ...' would indicate the allowed values. If not too many (only 2 in this case, I think), radiobuttons could be generated.  fg/bgcolor should have a color selector.  Lets make this a followup issue.

4. When changes take effect is another followup issue.  There are (at least) 3 possibilities.  Affect all open windows immediately.  Affect new windows in current session.  No effect until restart. (I think this should be avoided if possible, but I believe there are examples now).

It would be nice if ConfigDialog indicated somehow which.  If nothing else, this could be part of the missing Help (especially if specific to the current page).  Changes for the current window only should be only done by specific entries on the Option menu -- see below.

I think the proper answer depends on the option.  AutoComplete popupwait should take effect immediately.  Ditto for bgcolor, etc, for CodeContext.

On the other hand, CodeContext enable (for edit windows) should only affect new windows.  On the line-number issue #17535, I believe, we discussed the fact that the checkmark beside CodeContext on the Option menu has no relation to the current window and only refers to what will happen new windows.  My understanding of the consensus is that Option/Context should toggle and indicate the current window while the default for future windows should be changes by changing .cfg (with this editor).