To Add or Delete a Row or Column:

In the table, select a cell / column / row and a set of icons will appear. The first and second options are for column and row options.

The Insert option works based on where your cursor currently is. To add a row, select "Insert row above" or "Insert row below" . You could add an additional row and mark it as the header row by toggling the button at the first line of the menu.

The Delete function will delete the row or column that your cursor is currently in.

You have the same options when you decide to work on a column instead of a row.