my pleasure to make TileMill even better. The source I'm using
is a CSV file, with lat, lon and value_to_map. I guess I could
learn SpatiaLite if necessary, but it would be anyhow useful to
know why it doesn't work.
Best to you
Edit: Santa brought me good will. Acquired knowledge of
Spatialite, I can confirm this is a CSV input issue. Everything
works nominally with Sqlite. Happy Holidays!