I have a chart where there is a column of (parent) PRODUCT TYPE sorted by sales, and nested below are the (child) PRODUCT NAME.

I want to be able to show only the TOP20 selling (child) PRODUCT NAME under each (parent) PRODUCT TYPE, but still show all the (parent) PRODUCT TYPE.

Currently when I add the filter, it filters the (parent) PRODUCT TYPE TOP20 only. I need the sort to affect the child, not the parent.

New user here - If there is a link somewhere explaining how to do this I'd really appreciate a pointer.