I tried to construct the simplest filter, one hiding a single branch. I attached the Category Brainstorming Group 1 to the root of the branrch I wanted to hide. Then I set the condition as 'Categories' 'Do NOT include' 'Brainstorming Group 1." I would think that suffice to make the branrch and its children disappear, but not so.

Can someone tell me what I am doing wrong?