[Solved]-Heatmap yAxis change does not work as expected-Highcharts

The additional padding on y-axis is not added when you update axis extremes. As a solution change by 0.5 calculated extremes and disable properties: startOnTick, endOnTick.

thisHeatmap.yAxis[0].update({
    min: minValue - 0.5,
    max: maxValue + 0.5
}, true);

    yAxis: {
        ...,
        startOnTick: false,
        endOnTick: false
    }

Live demo: https://jsfiddle.net/BlackLabel/cjsmn0re/

API Reference:

https://api.highcharts.com/highcharts/yAxis

https://api.highcharts.com/highcharts/series.heatmap.rowsize