I can also confirm that this problem has been resolved for me as of a couple of weeks ago, I've been running 16.04 for a year now with this problem and using the nm-cli work-around until now:
network-manager 1.2.6-0ubuntu0.16.04.1 -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1542733 Title: Connect to Hidden Wi-Fi Network, "Connect" grayed out To manage notifications about this bug go to: https://bugs.launchpad.net/network-manager-applet/+bug/1542733/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs