I have looked over the software and I have been unable to find anykind of information to open a new tab when I make a request to Go & Fill a web site. Instead it opens in the current window. Am I missing a setting somewhere? Or is not available?
I'll pass your feature request along to the developers. For now you can only toggle the "New Window", "New Tab", and "Current Tab" setting in the 1Password extension in non-IE browsers.