POWER GEOPAK-EDIT ELEMENT

Hello,

I am learning Power Geopak V8i SS2.

I want to edit an element and use the first option: Slope Offset from Site Element and use Slope Variable.  There is a table to fill-out to define the variable slope but do not get that option, it is greyed-out.  How do I get the Table option so can use the Variable Slope option.  See attached image.