I have used Gmail manager forever. Unfortunately, the original creator no longer updates it, as far as I can tell, so it has fallen by the wayside. It was the perfect GMail Add On. I have tried every other option for GMail and the all suck. None of them work like Manager did. I imagine that the changes Google kept (keeps) making to mail made it impossible to keep up anymore. It's a shame we have been left with no valid GMail add-on options.