Quoting from the exchange portal's spatial heat map data function: "Studying raw point data for patterns can be difficult owing to uneven spatial coverage, and random variability in the values."
So the motivation is clear and the above data function is a good start but it is still very time consuming and error prone for the average user to manually add this data function every time you make a map chart and modify it every time you trellis differently and consequently want to split the data differently before running the data function.
It would be super cool, if the map chart for any given layer would have a check-box "Add heat map layer" just like you can add line fits to scatter plots (e.g. one per trellis panel) which would
a) automatically compute the required heat map data maybe with better performance than a data function (C# implementation?)
b) save it into a new data table and set up the required relations to the original table (just in case multi-layer trellising gets implemented at some point)
c) automatically add that layer to the map chart below the raw data layer