How to leave blank area in time header when group is collapsed

Sorry, I mean is it possible to leave this blank area when the group is collapsed?

At this moment, it's not possible. The area is added only when the vertical scrollbar is visible on the grid.

I made a wrapper for daypilot and override method _getScrollableWidth.

if (innerHeight > height && !autoHeight && this.reserveSpaceForScrollBar === undefined) || this.reserveSpaceForScrollBar) {
scrollBarWidth = DayPilot.swa();
}

var full = total - header - manualAdjustment - scrollBarWidth;
return full;

this.reserveSpaceForScrollBar - flag which I set when I need to have this blank space for the header.

Great, thanks for posting your solution!