public void setMenuSubGroup(String newSubGroup) {
		if (SystemUtilities.isEqual(menuSubGroup, newSubGroup)) {
			return;
		}

		if (newSubGroup == null) {
			newSubGroup = NO_SUBGROUP;
		}

		MenuData oldData = cloneData();
		menuSubGroup = newSubGroup;
		firePropertyChanged(oldData);
	}
Returns the group for the parent menu of the menu item created by this data.   That is, 
this value is effectively the same as {@link #getMenuGroup()}, but for the parent menu
item of this data's item.   Setting this value is only valid if the {@link #getMenuPath()}
has a length greater than 1.

@return the parent group
Ghidra/Framework/Docking/src/main/java/docking/action/MenuData.java