For this custom POI to load, it would need to be more like that: (custom zones in the newest version of NitroGen)
deco_copper_vein,BIOMEONLY,2,-10,1,11,1,custom_outback_size_3
deco_zinc_vein,BIOMEONLY,2,-10,1,11,1,custom_outback_size_3
To increase its amount, you can do something like this: (duplicate the lines, to increase the chance to show up)
deco_copper_vein,BIOMEONLY,2,-10,1,11,1,custom_outback_size_3
deco_copper_vein,BIOMEONLY,2,-10,1,11,1,custom_outback_size_3
deco_copper_vein,BIOMEONLY,2,-10,1,11,1,custom_outback_size_3
deco_copper_vein,BIOMEONLY,2,-10,1,11,1,custom_outback_size_3
deco_zinc_vein,BIOMEONLY,2,-10,1,11,1,custom_outback_size_3
deco_zinc_vein,BIOMEONLY,2,-10,1,11,1,custom_outback_size_3
deco_zinc_vein,BIOMEONLY,2,-10,1,11,1,custom_outback_size_3
deco_zinc_vein,BIOMEONLY,2,-10,1,11,1,custom_outback_size_3
The last entry is a zone, you could also add this to another zone like:
deco_copper_vein,BIOMEONLY,2,-10,1,11,1,custom_outback_size_3;downtown
to show up inside of cities