@kinokatsu,
To display indexLabel only for specific index value (in your case 1), you can check the index of the indexLabel in indexLabelFormatter function and display the same. Please take a look at the code snippet below.
indexLabelFormatter: function ( e ) {
if(e.index === 1 && e.dataPoint.dataPointLabel)
return e.dataPoint.dataPointLabel;
else
return " ";
}
Also, take a look at this JSFiddle for complete code.
—-
Manoj Mohan
Team CanvasJS