Question

After a chart has been inserted and formatted, is it possible to change the data range it refers to or to add new rows of data?

No, additional data cannot be included in a chart once it has been created; the user should delete the chart and create a new chart.
Yes, click the Select Data button in the Data group under the Design tab to extend or reduce the data range.
Yes, click the chart, select the additional rows or columns of data to add, and press Enter on the keyboard.
Yes, double-click the chart and select Properties from the list; in the Properties box, insert the new data range to include in the chart.

Answer 1

Yes — click the Select Data button in the Data group on the Chart Design (or Design) tab, then edit the Chart data range to extend or reduce the data included.