Is it possible to have the Soulbound enchantment be treasure loot only and not available from librarian trades?

In 1.20 versions of the mod, this should be doable through configs. In 1.21 minecraft moved a lot of enchanting to datapacks, and can be configured there. Let me know if you have specific questions on how to do certain things. If not, you can check the source of the mod and the minecraft wiki for reference