My approach would be very similar to the "HeatmapAnything" example Jason linked to in the post you linked.
location-tracking.fsm
The "Tracker" shape is responsible for most of the logic. In its reset trigger it maps grid cells (1m x 1m in this case) to the different planes in the "Zones" group. The code is pretty basic and assumes that the planes are all aligned with the grid, i.e. have a z-rotation of 0.
The code then runs the function stored in the "Update" label once. This function loops through the objects in the "TrackedTEs" group, determines their coordinates and sets their "Zone" label according to what those coordinates are mapped to. The function then calls itself in a fixed interval (0.1s in the attached model).
The "Zone" label on the operators being a categorical tracked variables enables tracking the time spent in each zone (like a state profile).
