Following formula can be used to calculate current "zoom points", these can be used to hide/show icons at the same thresholds as the native map icons:
800 * (1 / ctrlMapScale _ctrlMap) * (1 / getTerrainInfo#1)
The thresholds are defined in ptsPerSquare* ctrl map properties, e.g:
getNumber (configFile >> "ctrlMap" >> "ptsPerSquareObj")