Adding drag function to a polygon editor

Hi, Im writing a onscenegui polygon editor, trying to mimic the polygoncollider2D editor. I am using a FreeMoveHandle for each vertex (green) and there is a dotcap handle (shown in cyan) to show where new vertices would be placed

A new vertex is placed when the cyan dotcap handle is visible and the mouse button is clicked. This means i have to click to place, then click to drag the FreeMoveHandle of the new vertex.

This is pretty cumbersome and I really would like to just click and drag. Does anyone know how i could achieve this?

The code to add a new vertex is as follows;

                              Handles.color = Color.cyan;
                     Vector3 closestPoint = HandleUtility.ClosestPointToPolyLine(polygonArray);
 Handles.DotCap(0,closestPoint,Quaternion.identity,handleSize);
 
                     if(e.type == EventType.mouseDown && e.button == 0)
                     {
                         AddPoint(closestPoint);
                     }
 
                     Handles.color = Color.green;

and

 private void AddPoint(Vector3 pointToAdd)
 {
     m_PointCount.intValue++;

     int[] polygonEdge = FindEdgeByPoint(pointToAdd);

     for(int i = m_PointCount.intValue-2 ; i >= polygonEdge[1] ;i--)
     {
         SetPointArray(i+1, GetPointAtIndex(i));
     }

     SetPointArray(polygonEdge[1], pointToAdd);
 }