Managing Filters for Source Dimension

Summary: Is there a way to pick all zero level descendants of parent member I want to exclude from my entity dimension source. So If my top level entity is All Entities and under this is 50 sub rollups that each have 30 to 75 children. I want to exclude one of the 50 sub rollups and it's 40 children. In the add filters screen I don't see how to choose at zero level descendants of the sub parent I want to exclude. Seems like the only way to do this is to either pick the 49