Google Map Highlight the Path on Drag in the Route

Will this help you?

There were some abilities to Drawing on the Map https://developers.google.com/maps/documentation/javascript/overlays

Maybe this action will help you

There is a section Custom Overlays

https://developers.google.com/maps/documentation/javascript/customoverlays

Which is using OverlayView

The examples you can find here https://developers.google.com/maps/documentation/javascript/customoverlays

Also, there is the second way you can try Simple Polylines https://developers.google.com/maps/documentation/javascript/examples/polyline-simple

Here is the part of example

<script>

      // This example creates a 2-pixel-wide red polyline showing the path of
      // the first trans-Pacific flight between Oakland, CA, and Brisbane,
      // Australia which was made by Charles Kingsford Smith.

      function initMap() {
        var map = new google.maps.Map(document.getElementById('map'), {
          zoom: 3,
          center: {lat: 0, lng: -180},
          mapTypeId: 'terrain'
        });

        var flightPlanCoordinates = [
          {lat: 37.772, lng: -122.214},
          {lat: 21.291, lng: -157.821},
          {lat: -18.142, lng: 178.431},
          {lat: -27.467, lng: 153.027}
        ];
        var flightPath = new google.maps.Polyline({
          path: flightPlanCoordinates,
          geodesic: true,
          strokeColor: '#FF0000',
          strokeOpacity: 1.0,
          strokeWeight: 2
        });

        flightPath.setMap(map);
      }
    </script>