I just tried and it gave me an error of "access is denied".
I am currently connected via VPN so I do not know if that is why it says that (though I can browse smb fine) or if it is a true access issue. I will try again when I get home later today. This feature though is already part of the GUI, so the fact that I can not see my other volumes when I click the plus makes me wonder if there is a Channels coding limitation allowing you access to only the current volume because keeping in mind based on your images and my experience we can confirm channels CAN see the other volumes when you try and add custom content - so it is not a general NAS permissions issue, its a specific to the Channels "storage path" issue.
any insight @maddox?