Where can I get recipe to craft the skill crystals, I want to apply skill to all main character

You can't get it. It was only used to fix an issue a long time ago, but it's not obtainable anymore.

did I miss some recipes? or maybe it's still a skill crystal recipe issue?  I want to play like a collector with 100% completion and collection, please tell me to get it or please fix the list if I have collected everything