Canon EOS-1DX Instruction Manual page 363

w: Registering Custom Shooting Modes
My Menu settings will not be registered.
When the shooting mode is <w1>, <w2>, or <w3>, you cannot select
[54: Clear all camera settings] and [87: Clear all Custom Func.
(C.Fn)].
Even in the <w1>, <w2>, or <w3> shooting mode, you can still change
the shooting function settings and menu settings.
<w*> displayed on the top LCD panel together with the shooting mode
indicates that a registered Custom shooting mode is in use.
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