Adding and changing definitions in the matrix editor
To add a new definition of the type represented by the column or row
Right-click in any column in the matrix, and then click Add Column or Add Row. You are presented with a dialog that enables you to add a new definition of that type.
The new definition is added to the bottom of the list of matrix column or row definitions. To change its position, drag it to a new location.
To changing a definition in the matrix editor
To change a definition, right‑click a definition in a column or row, and select Modify Row or Column Definition.