Configuring intervals/line on y-axis

I know this can be done, but can’t see how!

On a view with time down the vertical axis, how can I configure this to show the faint grid lines at 15 minute interval?

Hello,
You can use hour_scale template to show an hour scale with 15 minute interval. There is an article:
https://docs.dhtmlx.com/scheduler/api__scheduler_hour_scale_template.html
One of the options is to create a cycle, which will be creating a div with a required time step:

scheduler.templates.hour_scale = function (date) {
    let step = 15;
    let html = "";
    for (let i = 0; i < 60 / step; i++) {
        html += "<div style='height:22px;line-height:22px;'>" + format(date) + "</div>";
        date = scheduler.date.add(date, step, "minute");
    }
    return html;
}

Please check the following example:
https://snippet.dhtmlx.com/tx1toaie