These verbal descriptions will disappear as soon as I've figured out how
to add a images to the dropdown box like in the fill/stroke dialog. I
succeeded in adding the widget from that dialog to the toolbar, but it
always appeared at the very end (I think even after the "style of new
objects" swatch) -- as if it was put outside some inner hbox containing
all the other widgets. Any ideas what that hbox would be and how to
access it? What precisely does the 'holder' refer to anyway that is
passed as an argument to all the toolbar prep functions?