Small working example
If you have a tank named tank and you want to pop a marker on it when destroyed it would be as follows.
name you tank tank
place a trigger
hint "tank destroyed!!"; marker = createMarker ["Destroyed",getpos tank];marker setmarkertype "DestroyedVehicle";marker setmarkersize [5, 5]; marker setMarkerColor "ColorRed"
Also you can set your markers invisible any time
The only thing to remember is that editor placed markers need the name in quotes created markers can use the created handle or the marker name
"Destroyed" setMarkerAlpha 0;
marker setMarkerAlpha 0;
0-1 sets the transparency.