Canon VB-R13VE Operation Manual page 146

Move the preview frame by dragging it and change its size by dragging the handles () positioned on its four
sides.
Note
To discard changes and restore settings saved to the camera, click [Clear]. However, note that mask area settings that have not
been saved in the camera by clicking [Apply] are all discarded.
3 Click [Apply].
The changed privacy mask area is saved to the camera.

Deleting a Privacy Mask from the Camera
Click [Delete] for [Mask area] in the privacy mask that you want to delete, then click [Apply].
The selected privacy mask area is deleted from the camera.
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