Don’t see the parent_sku column for import variables

Hi, and thanks for your plugin. I have successfully import a product with his attributes, but during the mapping I don’t see where to link “Parent_sku” to define variables. Actually my varaiations are imported like a simple product because I don’t set a parent. I see on the documentation a line “parent_sku” below the line “product_sku” but I don’t have the same on my administration. Could you help me please. Thanks