OK, I know Manager E from the Hicom 150 that I have. My first thought was to tell you to just look at all the feature codes that are defined in your system, but then I decided to throw this out there first....
You wouldn't happen to be asking about * 9 5 that gets you into programming mode, would you? One the 150 you do that and then enter a login and password.
Otherwise you can normally go in and look at what all the codes are for like silent monitoring, forwarding, etc if you have a non-display or analog phone, and you might be able to find what you're looking for on that list.