Well, C4 is a completely different approach. And actually a very good one if it really works without restrictions.
But Unity is different. They just use CG and you have to code shaders and their fallbacks the same as in gamestudio. The only difference which is quite nice, is that you can link to another shader for the fallback, so that different effects can share the same fallback without the programmer having to copy and paste the code. This results in more shaders, that include fallback, which is nice but doesn´t really make a big difference to gamestudio.
There are probably a few more differences, but they should all be small... At least I forgot them, after writing a shader in Unity a few weeks ago .

No, you're mixing two different concepts together. A visual editor is just for visual editing. For lighting, most engines use lighting modules from a shader code library. A7 does it this way and I bet C4 also. A7 shaders also work under all lighting conditions, fog, and so on. You only write the specific code for your shader. Writing code can't be done with a visual shader editor, thats why I prefer the A7 method.

It does work in C4 as far as I know from checking it some time ago.

It is still the same process of shader editing:



You have a lot of processes (basic, mathematical, complex and interpolant). And you connect these pre-defined processes in a similar way as you would program it in your code. It is just another kind of programming, a graphical approach just like Kismet is for Unreal or the graphical scripting approach in C4 (similar to the shader editor).

But the big difference is that it works on more than one platform. It does not matter what is behind these processes (CG, ASM or HLSL). Actually in C4 it is even more low-level than CG.