There is no keyboard shortcut for adding comments in Excel, but there are a few ways to make the process faster and easier. One way is to use the "Insert Comment" button on the ribbon. This button is located in the "Review" tab, in the "Comments" group. Another way is to right-click on a cell, and then select "Insert Comment" from the drop-down menu.
Once you have inserted a comment, you can quickly edit it by clicking on the cell that contains the comment. This will open the comment box, where you can make your changes. To delete a comment, simply click on the cell that contains the comment and press the Delete key on your keyboard.