Bows are now detected using NBTTags which means renaming a bow using an anvil won't create a custom bow
This is a change that will most likely break previously generated bows but due to recent changes in how display names are handled, it is nearly impossible to handle custom item checks through display names (lore is not an option either because lores do depend on the bow level).
You can now use {level} in the bows lores to display the bow level