Canon MG2400 series Online Manual page 156

To delete a cropping frame, click an area outside the cropping frame on an image.
In whole image view
To delete a cropping frame, select it and click (Remove Cropping Frame) on the
Toolbar. Alternatively, press the Delete key.
When there are multiple cropping frames, all the selected cropping frames (active
cropping frame and selected cropping frames) are deleted simultaneously.
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