I would like to recommend comboblock by pithy for those who like this idea, as it is a far better approach and, one can stack slabs atop one another all day :D
https://forum.minetest.net/viewtopic.php?f=9&t=15248
This mod adds stackable top slabs to Minetest.
*Depends = default
*Licence for the code = Minetest Game mod: stairs
=========================
License of source code:
-----------------------
Copyright (C) 2011-2012 Kahrl <kahrl@gmx.net>
Copyright (C) 2011-2012 celeron55, Perttu Ahola <celeron55@gmail.com>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
http://www.gnu.org/licenses/lgpl-2.1.html
*Licence for default textures = is under the license provided in Minetest default mod.
If there is something you would like to see added to this mod, i.e. support for other mods textures, or anything like that..., or if you have any issues with it, questions, ideas, or just like it..., please let me know.
Lots of new building options using the screwdriver : )
source = https://github.com/TumeniNodes/stackslabs
download = https://github.com/TumeniNodes/stackslabs/archive/master.zip
Install = rename file from "stackslabs-master", to only "stackslabs" and move into your mods folder. Be sure to enable the mod.
Enjoy