No it hasn't.

Nested Reports allows you to assign columns to arguments but DropDownDataWindow does not.

This still needs to be hand-coded, though a Service for this kind of cascading call should be relatively easy to create. Simply mimic what a user would need to do to make this happen.

Select line from dddw_1.
Get selected dddw_1 data values

Display dddw 2 values based on the value selected from ddw_1.

Select row from dddw_2.
Get selected dddw_2 values
.
.
.
and so on.

Olan