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Safety: Note and category creation could result in creating things that you don't need, or having the wrong names. However, this is undoable by renaming or deleting those items. A confirmation dialog is used before a delete to prevent accidental deletion. Photos in the camera roll can be deleted by selecting them and using delete/backspace, or by dragging them to the trashcan that appears at the bottom of the roll on dragging. Any mistakes that are made during text editing should be easily reversible by using the normal text editor functionality or using the undo/redo stream.
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