Ext based applications starts with main Ext.container.Viewport inside Ext.app.Application. The solution is to question the state of the application before the main Viewport is built. For example in my case I question the URL params . If in the params there is some param - in my case 'widget' I know that I need to build a single widget based on widget name from URL param (?widget='somewidgetalias'). I then create the widget by alias and a single widget viewport(regular viewport with no items) and I pass this created widget as item.
Ext.create('NG.view.WidgetViewport', {
items: [{
xtype: widgetName
}]
});
If I don't see the param in the URL , I continue to create a regular general viewport that creates the application. From the main application I open a new window with javascript like this : window.open(url, '_blank', specs);, the URL is the URL of the application and the param of widget='somewidgetalias' .