The way I do it is:
Click the selection in the browser, then hold the control button, and add the components you want to include. Then right click and select "Save Selection". You will then have 2 selections in the browser, then just delete the original. Kind of a pain, but seems to work for me.
Unfortunately, I believe that is the only solution in Publisher 2011. We are aware that this is currently a deficiency.
Autodesk Inventor ETO team