[Solved]-How to override Hihgchart.js Network Graph default node hover effect?-Highcharts

the simplest solution is to overwrite the default setstate function, example:

(function(h) {
  h.seriestypes.networkgraph.prototype.pointclass.prototype.setstate = function(state) {
    var args = arguments,
      point = h.point,
      others = this.isnode ? this.linksto.concat(this.linksfrom) : [this.fromnode,
        this.tonode
      ];

    if (state !== 'select') {
      others.foreach(function(linkornode) {
        if (linkornode && linkornode.series) {
          point.prototype.setstate.apply(linkornode, args);

          if (!linkornode.isnode) {
            if (linkornode.fromnode.graphic) {
              point.prototype.setstate.apply(linkornode.fromnode, args);
            }
                        
        /* modification - prevent hover effect on tonode
            if (linkornode.tonode && linkornode.tonode.graphic) {
              point.prototype.setstate.apply(linkornode.tonode, args);
            }
        */
          }
        }
      });
    }
    point.prototype.setstate.apply(this, args);
  }
}(highcharts));

live demo: https://jsfiddle.net/blacklabel/1039zwbt/1/

docs: https://www.highcharts.com/docs/extending-highcharts/extending-highcharts