Cluster Map Markers is available as part of the Premier plugin included with the Premier Subscription for Store Locator Plus. Cluster Markers show a single map marker graphics when two or more markers are within close proximity to one-another on the current map view. As a user zooms in the clusters break apart to show individual markers. When the zoom out the individual location markers combine into a single marker graphic with the count of locations represented by the graphic shown in the center.
Turn On Cluster Markers
Go to the Store Locator Plus Experience / Map tab and look in the Appearance section for “Enable Cluster Markers”.