@Override
	public String toString() {
		return Json.toString(this, "icon", "toolBarGroup", "toolBarSubGroup");
	}
Returns the subgroup string.  This string is used to sort items within a 
{@link #getToolBarGroup() toolbar group}.  This value is not required.  If not specified, 
then the value will effectively place this item at the end of its specified group.
@return the subgroup
Ghidra/Framework/Docking/src/main/java/docking/action/ToolBarData.java