mkgmap: filter points based on proximity

I modified the points file of my style to include traffic lights. Which adds an icon for each node with highway=traffic_signals set. When 2 divided roads intersect, and the turn lanes are drawn, it can result in a big cluster of icons.

highway=traffic_signals [0x6002 resolution 24]

Is there a way to display an icon only once if several identical points are within close proximity?

Hm, I don’t see a big cluster of icons in your screen shots. You ask about an option to display fewer icons, but the subject implies that you think about a new option in mkgmap to somehow detect this situation when creating the *.img files?
What would you want to get instead? What should happen when you zoom in?
Normally, the Garmin software decides what to render. Often there is an option to influence the level of details, but I don’t know if that helps in this situation.