Once you have added the upper and lower stiffener, you cannot add more horizontal stiffeners. In some cases, you want to add more than 2 horizontal stiffeners. In the example below, you might want to add an additional stiffener in the column at the beam’s flange.
First, add a diagonal stiffener to the column. Next, position this stiffener in such a way that is it horizontal and in line with the beam’s bottom flange.