The Vocabulary Tab
I do believe the new vocabulary tab was promised in April or early May. Any updates from the Duolingo staff? If it is going to be another month or so, please just be honest about it and say so.
I guess I joined Duolingo too recently to know that there had even been a vocab tab. It's definitely something that would make reviewing and retaining much easier.
Send in a support ticket. It generates an auto response and a ticket number. So someone has to read it at least. I'm not sure staff reads the forums unless they get flagged for profanity or something.
A few people are waiting until the end of May though. https://www.duolingo.com/comment/2993804