I am assuming you are talking about the new Attribute Table widget. The default config.xml does not have all the widgets listed to beincluded. You would either have to use config-all.xml or add the widgets you want in config.xml.
I meant in the viewer application. The Widgets tab that has the icons for each widget. The new ones are not in there.
Which new widgets are you refererring to? If it's the Attribute Table, this is not provided in the Widgets Tab, rather in the Layouts tab as referenced