Thanks! Unfortunately, this is a limitation of the blending options Godot exposes. Godot does have multiply blending, but its handling of transparency differs from what Spine requires. Screen blending isn't exposed at all.
Proper support would require Godot to expose the necessary blend settings. Shader workarounds are possible for some cases, but come with limitations, especially when blending overlapping transparent attachments. The “not yet supported” warning isn't a promise that these can simply be added to our shaders.
