Cannot remove matrix column

Added a subtotal to matrix column. But really wanted subtotal below the columns. Now that subtotal column is permanent. Cannot find a way to remove it.

Nevermind, just select subtotal on context menu again and it goes away. How obvious.

Still, after reading various posts here I realize that it's not obvious at all how to put column subtotals at bottom of a matrix. let's say I have a simple matrix with one row group and one column. All I want is to have total at bottom of each data column.