How to modify windows 10 Keyboard shortcuts?

One cannot change the Windows shortcuts, but one can intercept keys and change them on the fly.

AutoHotkey is a great program for remapping keyboard keys. Here are the steps to set this up:

1. Download and install AutoHotkey
2. Create a text file named startup.ahk and paste the following inside to map Ctrl+Alt+Right / Left to Ctrl+Win+Right / Left:

!^Right::^#Right
!^Left::^#Left

3. Save and run the script to test its functionality.
4. If it performs as expected, copy the script into the Startup folder

To find the startup folder in Windows 10, open "Run" (press Win + R, or search for it in the Start menu) and type either (without quotes): "shell:startup" for the current user, or "shell:common startup" for all users. Copy startup.ahk to the folder that opens.

I tried harrymc's script but it didn't work. So I modified it and the following one worked for me:

!^Right::send, #^{Right down}{Right up}
!^Left::send, #^{Left down}{Left up}

everything else was fine.

Then I improved the script by adding the following lines

!^Down::
    send, #^{Right down}{Right up}
    Sleep, 200
    send, #^{Right down}{Right up}
    return
!^Up::
    send, #^{Left down}{Left up}
    Sleep, 200
    send, #^{Left down}{Left up}
    return

This allows to emulate a 2x2 grid with UP and Down arrows to navigate between rows.

Edit: The sleep command was added to allow the animation to finish before sending the second send otherwise I have seen some occurrences where this second instruction was ignored.