diff --git a/Lib/idlelib/config-keys.def b/Lib/idlelib/config-keys.def
index f71269b5b49f46..700832c42ca7aa 100644
--- a/Lib/idlelib/config-keys.def
+++ b/Lib/idlelib/config-keys.def
@@ -44,9 +44,6 @@ find-in-files=<Alt-Key-F3> <Meta-Key-F3>
 find-selection=<Control-Key-F3>
 replace=<Control-Key-h> <Control-Key-H>
 goto-line=<Alt-Key-g> <Meta-Key-g> <Alt-Key-G> <Meta-Key-G>
-smart-backspace=<Key-BackSpace>
-newline-and-indent=<Key-Return> <Key-KP_Enter>
-smart-indent=<Key-Tab>
 indent-region=<Control-Key-bracketright>
 dedent-region=<Control-Key-bracketleft>
 comment-region=<Alt-Key-3> <Meta-Key-3>
@@ -104,9 +101,6 @@ find-in-files=<Alt-Key-s> <Meta-Key-s>
 find-selection=<Control-Key-s>
 replace=<Control-Key-r>
 goto-line=<Alt-Key-g> <Meta-Key-g>
-smart-backspace=<Key-BackSpace>
-newline-and-indent=<Key-Return> <Key-KP_Enter>
-smart-indent=<Key-Tab>
 indent-region=<Control-Key-bracketright>
 dedent-region=<Control-Key-bracketleft>
 comment-region=<Alt-Key-3>
@@ -164,9 +158,6 @@ find-in-files = <Control-Shift-Key-f>
 find-selection = <Control-Key-h>
 replace = <Control-Key-r>
 goto-line = <Control-Key-g>
-smart-backspace = <Key-BackSpace>
-newline-and-indent = <Key-Return> <Key-KP_Enter>
-smart-indent = <Key-Tab>
 indent-region = <Control-Key-bracketright>
 dedent-region = <Control-Key-bracketleft>
 comment-region = <Control-Key-d>
@@ -224,9 +215,6 @@ find-in-files=<Command-Key-F3>
 find-selection=<Shift-Command-Key-F3>
 replace=<Command-Key-r>
 goto-line=<Command-Key-j>
-smart-backspace=<Key-BackSpace>
-newline-and-indent=<Key-Return> <Key-KP_Enter>
-smart-indent=<Key-Tab>
 indent-region=<Command-Key-bracketright>
 dedent-region=<Command-Key-bracketleft>
 comment-region=<Control-Key-3>
@@ -271,10 +259,8 @@ find-again = <Command-Key-g> <Key-F3>
 find = <Command-Key-f>
 toggle-auto-coloring = <Control-Key-slash>
 select-all = <Command-Key-a>
-smart-backspace = <Key-BackSpace>
 change-indentwidth = <Control-Key-u>
 do-nothing = <Control-Key-F12>
-smart-indent = <Key-Tab>
 center-insert = <Control-Key-l>
 history-next = <Control-Key-n>
 del-word-right = <Option-Key-Delete>
@@ -288,7 +274,6 @@ copy = <Command-Key-c>
 paste = <Command-Key-v>
 indent-region = <Command-Key-bracketright>
 del-word-left = <Option-Key-BackSpace> <Option-Command-Key-BackSpace>
-newline-and-indent = <Key-Return> <Key-KP_Enter>
 end-of-file = <Control-Key-d>
 open-class-browser = <Command-Key-b>
 open-new-window = <Command-Key-n>
diff --git a/Lib/idlelib/config.py b/Lib/idlelib/config.py
index 04444a3bf20b30..e4fc7da84ca36f 100644
--- a/Lib/idlelib/config.py
+++ b/Lib/idlelib/config.py
@@ -634,9 +634,6 @@ def GetCoreKeys(self, keySetName=None):
             '<<find>>': ['<Control-f>'],
             '<<replace>>': ['<Control-h>'],
             '<<goto-line>>': ['<Alt-g>'],
-            '<<smart-backspace>>': ['<Key-BackSpace>'],
-            '<<newline-and-indent>>': ['<Key-Return>', '<Key-KP_Enter>'],
-            '<<smart-indent>>': ['<Key-Tab>'],
             '<<indent-region>>': ['<Control-Key-bracketright>'],
             '<<dedent-region>>': ['<Control-Key-bracketleft>'],
             '<<comment-region>>': ['<Alt-Key-3>'],
diff --git a/Lib/idlelib/editor.py b/Lib/idlelib/editor.py
index fcc8a3f08ccfe3..91896fc58c5f13 100644
--- a/Lib/idlelib/editor.py
+++ b/Lib/idlelib/editor.py
@@ -299,6 +299,12 @@ def __init__(self, flist=None, filename=None, key=None, root=None):
         self.askyesno = messagebox.askyesno
         self.showerror = messagebox.showerror
 
+        # Bind keys to pseudoevents for non-configurable key-specific handlers.
+        text.event_add('<<smart-backspace>>', '<Key-BackSpace>')
+        text.event_add('<<newline-and-indent>>',
+                       '<Key-Return>', '<Key-KP_Enter>')
+        text.event_add('<<smart-indent>>', '<Key-Tab>')
+
         # Add pseudoevents for former extension fixed keys.
         # (This probably needs to be done once in the process.)
         text.event_add('<<autocomplete>>', '<Key-Tab>')
diff --git a/Misc/NEWS.d/next/IDLE/2021-05-28-09-28-45.bpo-43654.WYsKKG.rst b/Misc/NEWS.d/next/IDLE/2021-05-28-09-28-45.bpo-43654.WYsKKG.rst
new file mode 100644
index 00000000000000..8f4e10beed892b
--- /dev/null
+++ b/Misc/NEWS.d/next/IDLE/2021-05-28-09-28-45.bpo-43654.WYsKKG.rst
@@ -0,0 +1,5 @@
+Fix the config dialog breaking tab completion.  This is achieved by removing
+the key configuration options for ``<<smart-indent>>`` (Tab),
+``<<newline-and-indent>>`` (Return, Enter) and ``<<smart-backspace>>``
+(Backspace) from the configuration mechanism, making them hard-coded
+instead.