import it into Unity, the material cannot be automatically created.

626441769

I set the addition mode in Spine, but when I import it into Unity, the material ball cannot be automatically created.
the screen mode I set in the same way can be automatically created.

Misaki

626441769 This is one of the advantages of using Premultiply Alpha. When textures are packed with Premultiply alpha, they can be covered with normal material up to the Additive blend mode. This reduces the number of draw calls, which in turn reduces the rendering load. This is described in the following section of the spine-unity runtime documentation:
spine-unity 运行时文档资产 #进阶操作 - Premultiplied和Straight Alpha导出

626441769

That is to say, in Spine, I created materials with Normal, Additive, Multiply, and Screen modes simultaneously. After importing them into Unity, only the SkeletonPMAMultiply corresponding to the Multiply Material, the SkeletonPMAScreen corresponding to the Screen Material, and the material for the Normal mode can be created. However, the additive material cannot be created.

Misaki

626441769 When using PMA textures, it is standard practice to use the same material for both Normal and Additive blend modes, so materials for Additive blend mode are not automatically generated. If you need a material for Additive blend mode for some special reason, you can create it yourself.

626441769

I've found the settings here. That means, when I use the additive mode, do I need to manually click here to create the material every time I import it into Unity?

Misaki

626441769

That means, when I use the additive mode, do I need to manually click here to create the material every time I import it into Unity?

If you simply want to replicate the appearance of additive blending in Spine rather than edit the additive material itself, then such manual settings are unnecessary.
To reiterate, the advantage of using PMA textures is that additive materials are not required in the first place.
The following thread may be helpful in understanding the advantages of textures that use Premultiplied Alpha:
https://esotericsoftware.com/forum/d/3132-premultiplied-alpha-guide