Higcharts Gantt chart with table and sub-tasks - highcharts

Question

How can I have collapsible sub-tasks while using the table on the left? If I remove the table columns then it works fine. This is the example from the official website, unfortunately there is no demo for my case. Any guidance is appreciated.
Here is the fiddle I've played with: https://jsfiddle.net/sharvadze/4h80gdts/1/
Highcharts.ganttChart('container', {
title: {
text: 'Left Axis as Table'
},
xAxis: {
tickPixelInterval: 70
},
yAxis: {
type: 'category',
grid: {
enabled: true,
borderColor: 'rgba(0,0,0,0.3)',
borderWidth: 1,
columns: [{
title: {
text: 'Project'
},
labels: {
format: '{point.name}'
}
}, {
title: {
text: 'Assignee'
},
labels: {
format: '{point.assignee}'
}
}, {
title: {
text: 'Est. days'
},
labels: {
formatter: function () {
var point = this.point,
days = (1000 * 60 * 60 * 24),
number = (point.x2 - point.x) / days;
return Math.round(number * 100) / 100;
}
}
}, {
labels: {
format: '{point.start:%e. %b}'
},
title: {
text: 'Start date'
}
}, {
title: {
text: 'End date'
},
offset: 30,
labels: {
format: '{point.end:%e. %b}'
}
}]
}
},
tooltip: {
xDateFormat: '%e %b %Y, %H:%M'
},
series: [{
name: 'Project 1',
data: [{
id: 'test',
start: Date.UTC(2017, 10, 18, 8),
end: Date.UTC(2017, 10, 25, 16),
name: 'Start prototype',
assignee: 'Richards',
y: 0
}, {
parent: 'test',
start: Date.UTC(2017, 10, 20, 8),
end: Date.UTC(2017, 10, 24, 16),
name: 'Develop',
assignee: 'Michaels',
y: 1
}, {
start: Date.UTC(2017, 10, 25, 16),
end: Date.UTC(2017, 10, 25, 16),
name: 'Prototype done',
assignee: 'Richards',
y: 2
}, {
start: Date.UTC(2017, 10, 27, 8),
end: Date.UTC(2017, 11, 3, 16),
name: 'Test prototype',
assignee: 'Richards',
y: 3
}, {
start: Date.UTC(2017, 10, 23, 8),
end: Date.UTC(2017, 11, 15, 16),
name: 'Run acceptance tests',
assignee: 'Halliburton',
y: 4
}]
}]
});