Change individual armor pieces registry name

You can change the registry name of the all armor at one (ruby_helmet, ruby_chestplate, ...) but not for only one piece.
To change it, you need to go to the left, there is an icon with a square and "ID" inside. You select your armor mod element, then you click on this button with ID and the square, and you rename the ID "ruby_" and then, every piece of your armor will be like "ruby_chestplate", "ruby_boots", ...