I haven't found that one either. I don't think it exists.
Try setting the sequence In point (by pressing the I-key) when you set the beginning of the work area, and then set the sequence Out point (by pressing the O-key) when you set the end of the work area. This presupposes that the CTI is parked where you want the workspace to begin and end.
Not only can you then get from sequence/work area in/out by pressing the Q/W keys, you can also set up a playback loop in the Program Monitor.