In the datasheet, "Undo" (Ctrl+Z) does not work

Solution

You can always undo the changes in PowerPoint. Close the datasheet to return to PowerPoint and click the Undo button on the Quick Access Toolbar (or press Ctrl+Z ). The chart on the slide will revert to its previous state, and the changes in the chart's datasheet will be undone accordingly.

Explanation

think-cell's datasheet is an Excel sheet. The datasheet is saved whenever the PowerPoint slide is updated after you changed some data. Unfortunately, Excel always discards its undo-buffer on save. You can experience the same behavior when working directly with Excel after saving the workbook.