How to remove this quick-access widget on Redmi?

On my friend's Redmi 7A phone, this widget newly appeared on the home screen, probably after a system update. It looks like a little white arc or fingernail clipping on the screen border. Pulling it out shows a circular button with a circle symbol, and tapping that gives the array of buttons in the pic below. We could not identify it in the widget list (homescreen long tap), it cannot be dropped onto the Delete caption, and Google Lens found no instance of my picture. How to get rid of this?