Hide the Source Monitor
You probably know that the Composer Window can be resized, but did you know you can completely hide the source monitor? This can be very helpful if you’re short on screen real estate and want to work on a visual effect where you need to make things big — an Animatte, for example.
To hide the source monitor, Option-click (or Alt-click) the Source/Record Mode button at the bottom of the timeline. Then enlarge the Record monitor by right-clicking it and selecting Full Size Video. Or you can simply resize the Composer window by dragging its bottom right corner — if you drag it into a roughly square shape the source monitor will disappear.
To restore the source monitor, option-click the Source/Record button again, or drag the monitor into a wide rectangle.
You’ll probably want to memorize your custom window setup in a Workspace or Toolset. See this video tip for details.