src/vs/workbench/browser/parts/editor/editorPart.ts/EditorPart/doAddGroup
class EditorPart:	private doAddGroup(locationView: IEditorGroupView, direction: GroupDirection, groupToCopy?: IEditorGroupView): IEditorGroupView {
		const newGroupView = this.doCreateGroupView(groupToCopy);

		// Add to grid widget
		this.gridWidget.addView(
			newGroupView,
			this.getSplitSizingStyle(),
			locationView,
			this.toGridViewDirection(direction),
		);

		// Update container
		this.updateContainer();

		// Event
		this._onDidAddGroup.fire(newGroupView);

		// Notify group index change given a new group was added
		this.notifyGroupIndexChange();

		return newGroupView;
	}