> Since it is my fix, I will write the PR.  But first, please test part 2, changing '0' to '0:1', just to make sure it works.

Just tested it and it works fine with slice. Please find the respective diff and options menu displayed as below : 

git diff | cat
diff --git a/Lib/idlelib/macosx.py b/Lib/idlelib/macosx.py
index 9be4ed2ec4..16a13a0f2e 100644
--- a/Lib/idlelib/macosx.py
+++ b/Lib/idlelib/macosx.py
@@ -178,7 +178,7 @@ def overrideRootMenu(root, flist):
     del mainmenu.menudefs[-1][1][0:2]
     # Remove the 'Configure Idle' entry from the options menu, it is in the
     # application menu as 'Preferences'
-    del mainmenu.menudefs[-2][1][0]
+    del mainmenu.menudefs[-3][1][0]
     menubar = Menu(root)
     root.configure(menu=menubar)
     menudict = {}

Options menu
- Show code context (disabled)
- Zoom height

git diff | cat
diff --git a/Lib/idlelib/macosx.py b/Lib/idlelib/macosx.py
index 9be4ed2ec4..d6a1b376a1 100644
--- a/Lib/idlelib/macosx.py
+++ b/Lib/idlelib/macosx.py
@@ -178,7 +178,7 @@ def overrideRootMenu(root, flist):
     del mainmenu.menudefs[-1][1][0:2]
     # Remove the 'Configure Idle' entry from the options menu, it is in the
     # application menu as 'Preferences'
-    del mainmenu.menudefs[-2][1][0]
+    del mainmenu.menudefs[-3][1][0:1]
     menubar = Menu(root)
     root.configure(menu=menubar)
     menudict = {}

Options menu
- Show code context (disabled)
- Zoom height