The Communicate window is an overgrown blob.
Fortunately you can vote on Jira to get it to be better:
Please vote on Jira:
https://jira.secondlife.com/browse/VWR-1076
and a similar:
https://jira.secondlife.com/browse/VWR-1550
you can vote for as many issues as you like when you are logged in.
Like many people who manage large groups or have customers, I have a constant stream of new IM coming to me while I am logged into SL. The current Communicate window forces me to drop everything I am doing to answer IM, and all I can do is stand there blind and mute while nothing but IM covers the screen. If I need to attend to the chat coming to me from nearby people, I am forced to ignore the IM. This makes no sense.
I need to be able to separate chat history, IM tabs, the friends list, and the volume controls into four separate, size and shape changeable, potentially very small windows. This way, I can track them all at once. I especially need to be able to view chat history and the IM sessions I am in, at the same time, without having to toggle between them.
Also, it is very unlikely that once I am in a text IM session with someone, I am going to be using voice with them, and much more likely I will use voice with one person at a time, so there's no reason to attach a huge volume control to anything having to do with text. Possibly a tiny button that could be expanded if needed, would make more sense.
Imagine what it would be like to have someone open up a new IM with you every five minutes, until you have six or twelve IM sessions going on at the same time, while still having to chat with the people next to you, and you will have some idea of what I deal with frequently. All this while still having to see where I am going walking around, too. The old interface was tolerable for this, but the Communicate window is impossible. It gives me the impression that the designer never thought you would talk with more than one person at a time.