Additive Render Mode in Java Edition

It would be nice to have a way to create custom textures with the Additive render mode in Java. This feature can be found in Bedrock Edition on several community maps, allowing map creators to deliver content with greater visual quality and fidelity to their concept arts.

Also, making it easier to define whether texture will be Default, Emissive or Additive without having to rely on the vanilla shader-core to change hardcoded values it would be nice.