To Add or Delete a Row or Column:
In the table, select the row or column after which you want to add or delete one and a set of icons will appear. You can also perform other activities in that section
To add a row, select "Insert row above" or "Insert row below" based on your needs. You could add an additional row and mark it as the header row by toggling the button at the first line of the menu. Also you can delete such row or select it for additional actions.
You have the same options when you decide to work on a column instead of a row.
When creating a new row or column it will be created at the desired position and the editor will be ready for you to add content to it.