How do I customize the user interface for the desktop client?

Dear Rainbow

How do I customize the user interface for the desktop client for Rainbow?  Currently, when maximized, there is a lot of wasted screen real estate down the sides, but in the middle, the sub-window showing the participants covers up most of the sub-window for the messages, making it difficult to see the messages when there are a lot of them.

Then, when maximizing the sub-window when someone is sharing their desktop or one of their applications, this sub-window covers everything else.  It should be possible to arrange these sub-screens so that the user can see the shared desktop/application at the same time as the messages and the participants.

Thank you

Antony