Currently, a "Lobby" for use as a waiting area for participants as they join is only a feature of Personal Rooms. For scheduled meetings, there is a Lobby, but it cannot be used as a waiting area for joining participants. As a host, you may right click on a participant and move then into the Lobby, but that's the extent of the Lobby support for scheduled meetings.
Please expand the Lobby/Waiting Room function to all scheduled WebEx meetings, not just the Personal Room.
How I'd see this best functioning would be that, if the host "locks" the meeting, any joining participants would be placed in the Lobby instead of being blocked from joining. Then the host would be able to release participants into the meeting room from the Lobby as they see fit.