Static Switch

That gives the same result as the OT, but it still leaves all the calculations in the shader code, basically calculating the "other branch" for nothing.

I also like the feature of having compile-time switches to just disable certain shader features for different materials.

It is not possible to have multiple switch with the same variable like in U4?
I would like to use the same switch exposed to make different logics on the shader.

Is the static switch that remove the calculations of the disabled branch not planned any more?

Currently not I'm afraid, as mentioned above

Is there any chance/way to expose the "Blend mode" of a shader (from the shaderforge shader editor window) into the actual compiled shader? I feel it's kind of redundant having to create 3 versions of a particle the shader for additive/multiply/alphablended versions.