In the PRO version of the plugin, you can create clusters of round markers when there are too many markers close together. This feature is currently only available for the round coloured markers.
You simply need to enable the ‘Cluster Markers’ option in the ‘Round Markers’ tab of your map and the following panel of options will become available:
This feature is not very advanced, it will simply create clusters based on the distance between the markers and the ‘threshold’ provided by you. A bigger threshold will mean the markers will be grouped considering longer distances between them. Smaller values will look for markers closer by. Usually values between 0.1 and 1 will work better. Considering the size of the maps, thresholds above 3 will most likely simply group all markers, or most them, together. All markers will then display at a zoom level manually defined by you. These values are mandatory for the clustering to work properly.
If you have a lot of markers, it’s likely that the clustering option will slow down the map initially, since they need to be processed on the fly, when the map initially load. This option should not be used as a way to speed up the maps, it will actually have the opposite effect.