Mixed reality (MR) environments provide great value in displaying 3D virtual content. Systems facilitating co-located multiuser MR (Co-MUMR) experiences allow multiple users to co-present in a shared immersive virtual environment with natural locomotion. They can be used to support a broad spectrum of applications such as immersive presentations, public exhibitions, psychological experiments, etc. However, based on our experiences in delivering Co-MUMR experiences in large architectures and our reflections, we noticed that the crucial challenge for hosts to ensure the quality of experience is their lack of insight into the real-time information regarding visitor engagement, device performance, and system events. This work facilitates the display of such information by introducing immersive in situ visualizations.