halfway, there are labels with icons. The icon and the string are objects, not widgets, whereas the Button for Tabbed contains a Kill-Button within itself, next to the String (-object)
if useful, space can be done (external space) per child, as well as (internal space) by the widget. That's nasty, since it has the same name. Perhaps the Layout should have those values, not the Widget?
Should there be widgets like VList, or only Layouts like VLayout? How would you ever translate that to XML?