hey, one of the devs here! The composer control panel in Cmd-Shift-I was experimental and we were learning how people use composer best. The best part about it was being able to review things quickly, and we partially allow you to do that inside the composer window itself, and in future updates we will make it easier to review things even more.
If you really liked the control panel mode because it was full-screen, I recommend popping composer into an editor and making that full-screen!
Do you think there is a usecase that is not covered in the above?