The portal example is very "outside" of the Ext JS proper..there is a lot of custom components and logic involved to power the Portal example. Likewise with the explorerview example, which is a custom grid view. Generally, these types of comopnents that are far outside the "out-of-the-box" boundaries can only be built by hand. The Designer is being architected to support the import & use of such custom components on the Designer canvas. But to actually build such components is not a task for the Designer.
I hear you man...! I expected that anyway, but I simply cannot wait to have the components imported in the near future...! It would be giving so much more value to the designer...!
By the way - I have been bugging the extjs dev team for quite sometime now! Any chance one could have the browser-like panel built INTO the core?
I tell you why - because when new versions of ExtJS appears then the component might break-up because it is a third party. I find it a rather useful feature for application layouts...!