Some of the monitor's are missing from the GUI?

In the Monitor documentation for MFIX : 4.11. Monitors — MFiX 19.3.0 documentation

There is mention of an Area Monitor : This can be used to find the actual meshed area of the inlet/outlet.

I want to set up this monitor at my inlet and outlet pipe so that I can measure the actual meshed facet area.

However, this monitor is not present in the list of monitors in the GUI.

Screenshot (7)

Is there something I am missing or doing wrong?

The documentation is misleading. The Area and Volume are not actually monitor outputs but intermediate variables used in the computations of other monitors. We can expose them in a future release.

You can see the area of a BC region by inspecting the .OUT file and going to the Boundary condition section.