there are some great tips here: https://forum.inaturalist.org/t/in-pursuit-of-mappiness-part-1/21864 and here https://forum.inaturalist.org/t/hotspot-view-for-species-genera-families-etc-taxon-not-just-for-users-and-places-projects/38264
It’s a map that shows higher density of observations though, not species necessarily. To do the latter I think you’d need to do some more work with external tools.