How find and change a keyboard shortcut?

On Sonoma. Have been editing my keyboard shortcuts and made a mistake I can't fix. Each time I press the shift key (i.e. the one for upper case letters), all open windows slides out from the display. When I let go from the key, they slide back again.

Have been sitting a hour trying to find the shortcut I edited that causes this, but miserably failed. I have turned off and on every shortcut I can find and tested. No go.

How can I find it?