It might be possible to make a datapack of custom potions but I am not a big of a programmer or coder. So, if you know someone who knows to code professional datapacks, then be sure to ask them about it.
See RADI0R It is possible to do that with MCreator but, you need to make it as a mod, not a datapack. MCreator has its own mod workspace where you can make custom potions.