I'd rather have a separate window with a treeview like the hierarchy window

That's a good point. So who's played with DAZ Studio? There IS a popup you can use, if you want; but there's also a dockable palette with a hierarchical list of everything in the file; and of material zones in a figure; etc. In fact, I might be using DAZ Studio much more than I do (and likely more than Poser), except that I will not give up dynamic hair and clothing.