Enchantments in latest snapshot

Hi! Just been investigating the new enchantment system in 24w18a. I can't figure out how to add/modify enchantments. I've tried:

Adding a new enchantment under the minecraft namespace
Adding a new enchantment under a different namespace
Overriding an existing enchantment under the minecraft namespace (can you even directly override vanilla files? Not sure.)
My data pack works with other features - e.g. I can add a simple loot table that works, it appears in /datapack list. After decompiling the server JAR I noticed that one class still lists all the vanilla enchantments. Maybe they're still registered in code as well as being data driven? Any help/suggestions greatly appreciated.