Excel Online doesn’t have the Resize Table option but you can manually resize your table by adding columns and rows.
To add a new column to your table, type data in the column to the right of your table and press Enter.
To add a new row, type data in the row below the last table row and press Enter.
Note: New columns and rows might take a few seconds to appear inside the table.
If you need to add a large number of columns and rows, you’ll find it easier to use the Resize Table option in the Excel desktop application. If you have the Excel desktop application, click Open in Exceland use the Resize Table option under Table Tools. There are more details here.
When you save the Excel desktop workbook and reopen it in Excel Online, you'll see the changes you made.
For news about the latest Excel Online updates, visit the Microsoft Excel blog.