TradeManager 2009 can merge conversation windows into one window, but not available in community chat. It is much more convenient for chatting with several contacts. The operation steps are as follows:
Left click the title bar of a certain conversation window, and drag it to another conversation window. Then it will show up a "Merge induction area".

Then left hold down the mouse, and more the mouse over the "Merge induction area". When the "Merge induction area" turns to yellow-green, please rest the mouse. The conversation windows will be merged into one window.

The merged box is as follows:

Or set "Merge conversation windows" function as defaults. Please take the following steps:
Please go to Menu > Preferences > General > Message Options and select "Merge Multi Windows".

Thus, when you chat with several contacts, all the conversation windows will be merged into one window.