To duplicate an existing chart, click into the chart cell that contains the chart you wish to copy.
Click the ‘Chart Tools’ icon at the top-right of the cell and then click the ‘Edit chart’ icon.
Click into the Chart name field at the top of the screen and give the chart a new name.
Click the copy icon next to the Save icon. This will create a duplicate of the selected chart; the current chart will remain unchanged.
When a chart is duplicated, the duplicated copy is placed into the Chart Library. The chart that was originally in the cell will remain unchanged.