Seems a bit odd but, for Link type packages, you define where it goes in the distribution package itself. You have the option to place it on the Desktop, LaunchPad and\or Start Menu.
I just ran a quick test and was able to have it show up on the Portal by selecting "LaunchPad" in the distribution package under the "Link location" section.
Hope this helps answer your question.
A bit disjoined and confusing, but I guess it ultimately makes sense. Seems to work as you describe. THANKS!