Excel Online doesn’t have the font orientation option for you to apply vertical fonts or rotate fonts in an angle.
If you have the Excel desktop application, you can use it to open your workbook and change font angles. Here’s how:
Click Open in Excel and follow the steps in Rotate or reposition data in a cell.
Note: You won’t be able to see the changes when you reopen the workbook in Excel Online since it isn’t supported.
For news about the latest Excel Online updates, visit the Microsoft Excel blog.