Canon EOS R3 Advanced User's Manual page 441

Note
To clear registered AF points, hold down the < > button and press the < >
button, or press and hold the < > button.
You can also clear registered AF points by clearing all camera settings.
You can register separate home positions for each camera orientation when the
orientation-linked AF point setting ( ) is set to [Separate AF pts: Area+pt] or
[Separate AF pts: Pt only].
Although it has no effect if you attempt to register a home position while a subject is
being tracked with a tracking frame, you can clear registered positions at this time.
441