The code contains
Code:
action.py: dont_add_to = frozenset(['menubar-device', 'toolbar-device', 'context-menu-device'])
so I think it is working as designed; no ability to add it to the "Toolbar when a device is connected"
What you could do is to add it to the "The optional second toolbar" which is displayed at the bottom of the screen (and is the same whether or not a device is connected).