The Transcript Window contains messages detailing the actions performed by Control Center while carrying out your commands. You can show or hide it from the Menu Bar by toggling View => Show Session Transcript.
Some of the events reported are the beginning and end of command execution (with an indication of success or failure), changes to system configuration files, and warning or error messages regarding exceptional situations encountered by the tool.
Some of those messages may not be reported to you by any other means (such as in the Status Bar or in pop-up dialogs), so this represents a higher verbosity level. These additional messages may be related to situations where Control Center was able to recover from an exception and proceed without human intervention or where the exception was expected (such as not being able to read configuration files for a non-initialized Cluster). They can also be only informative messages indicating what has been changed in the system by the tool.
Due to a implementation restriction in this release, the contents of the Transcript Window are not updated in real-time, but only after the requested command finishes executing. It is intended to be used as a history-like feature, not as a progress indicator. Do not assume Control Center is stalled because you do not see new messages appearing in the Transcript Window.