Canon EOS R3 Advanced User's Manual page 521

2.
Select [Select images].
3.
Select the image to protect.
Turn the <
4.
Protect the image.
Press <
with a [
To cancel protection and clear the [
To protect another image, repeat steps 3 and 4.
Note
During playback, you can protect images by pressing the <
> dial to select an image to protect.
> to protect the selected image, after which it will be labeled
] icon (1) at the top of the screen.
521
] icon, press < > again.
/ > button ( ).