ah yes! You mean HIDDEN MARKERS
"MarkerName" SetMarkerType "Empty" (thats the hidden one)
and then ia WP/Trigger, put:
"MarkerName" SetMarkerType "Flag"
yer choise, mayo!
Just use the "Set marker type" command. Type may be any of:
"Flag", "Flag1", "Dot", "Destroy", "Start", "End", "Warning",
"Join", "Pickup", "Unknown", "Marker", "Arrow", "Empty".