Fantastic crafting system! I'm more of a fan of ingredient based crafting susch as those in Paper Mario and BOTW than recipe based systems but they were almost impossible to find plugins for.
One question though, which lines in the plugin do I comment out // if I would like to hide the fourth slot completely from being selected? I don't plan on using it at all. Currently I'm leaving the name blank to "hide" it but preferably remove it completely so it's one less line to scroll down to get to the craft confirm.