Duplicate column

Open the chart you want to edit.
In the upper-right corner, click EDIT.
In the bottom-right corner, click DATA.
Next to the column name you want to duplicate, click the more icon .
Click Duplicate.

To rename the column you duplicated, double-click on the column header or click the more icon next to the column name, then click Edit column. Enter the new name under Column, and hit SAVE.

Duplicated columns will not be automatically plotted as series in your chart. Instead, you will need to add it manually.