Although I copied the action-file to Designer/addons-folder, the actions aren't recognized in the rules-files. So the designer shows errors, where aren't errors at all, also the auto completion does not work (evident)
This Problem exist at least with Win7-64, Oracle Java7u67-32 and with openHAB nightly build 716 or older. With the same Installation, xmpp-action works as expected, so I think, the problem could be in squeezebox-action-file.

See also http://knx-user-forum.de/openhab/35875-designer-meckert-squeezebox-actions.html