The information that the user did something "right" should be responsive next to where the user initiated the action- not in a random corner.

That control may not be visible by the time the operation completes.

Toasts are popular, but not the only option if you want to notify the user about completion of a longer-running action when the user may have already switched away from where they started it. Consider a status bar[0] instead. You can make it cute and animated, too!

[0] https://developer.mozilla.org/en-US/docs/Web/Accessibility/A....

There are certainly times where this must be the case, but I think it's broadly better to have designs avoid this.

That’s why confetti exists