So I checked previous questions regarding this, which all relate to V2, which is of no help.
So, I create two markers, save them in an array as markers[\"to\"] and m
Assuming that "mypolyline" is your Polyline object, you can also try:
mypolyline.setPath([]);
This way, you are taking out the coordinates from the Polyline, which in effect will remove it from the map.