: <traceback-gadget> ( model -- gadget )
    [ vertical traceback-gadget new-track ] dip
    [ >>model ]
    [
        [ horizontal <track> ] dip
        [ <datastack-display> 1/2 track-add ]
        [ <retainstack-display> 1/2 track-add ] bi
        1/3 track-add
    ]
    [ <callstack-display> 2/3 track-add ] tri
    add-toolbar ;