How to set the category programmatically in the suggestions window?

Is there a way to set the category programmatically in the suggestions
window? By category, I mean the type of filter where you right-click in the
suggestions window, and select an item from the Show menu. We need this,
because we want to filter all suggestions so that only those from one
category show in a flat list. The problem is that the filter mechanism
starts with All categories, and our category shows up as a parent node in
the suggestions window. The filtering mechanism doesn't work in this case,
and anyway we want to show all the suggestions in a flat list.

Thanks,
Julian Sinai