the title says all,
like in the old original ex nihilo that you can add custom recipes to the crucible using zenscript, and maybe add a "only with that heat" statement? so one can make that an object require more heat than others to liquify (sry for the english, i'm not too good :D)

In creatio a lot of things can be configured using the json files. Enable json in the config: start/stop the game. Edit the json files that were generated in the config/exnihilocreatio folder.