In Minecraft 24w18a, it seems that we can add custom enchantements with a file like this (this one is a vanilla one, sharpness)
but there's more complicated stuff like frost's walker one :
frost_walker.json
Theses one come from the vanilla server jar at this path :
server.jar\META-INF\versions\24w18a\server-24w18a.jar\data\minecraft\enchantment\
In Minecraft 24w18a, it seems that we can add custom enchantements with a file like this (this one is a vanilla one, sharpness)
but there's more complicated stuff like frost's walker one :
frost_walker.json
Theses one come from the vanilla server jar at this path :
server.jar\META-INF\versions\24w18a\server-24w18a.jar\data\minecraft\enchantment\