Can't reassign "ctrl +z" and "ctrl + y" keybinds on a Swiss QWERTZ keyboard

[guiguismall]

Godot version:
Godot Engine v3.2.3.stable.mono.official

OS/device including version:
Windows 10 Education N
Version 1903
Swiss Keyboard (the "Y" and "Z" keys are inverted)

Issue description:
Changed the keyboard shortcuts for "undo" and "redo". They accept the new keybinds, but the old ones ("ctrl + z" and "ctrl + y") remain active too.
Assigning "ctrl + z" and "ctrl + y" to different commands does not help, they remain bound to the "undo" and "redo" commands.

Note: The reason I want to reassign those keybinds is to invert them. the "Z" key is very far from the "ctrl" key on my swiss keyboard, making using the "undo" command painful in the long run.

Steps to reproduce:

1. Try to assign "ctrl + Z" and "ctrl + Y" keybinds to different commands
2. that's it

Minimal reproduction project:
HelloGodot.zip