UE translates shader graphs to HLSL - high level shading language, see:

https://dev.epicgames.com/community/learning/knowledge-base/...

Shadertoy needs GLSL - open gl shading language. Luckily, UE has a HLSL -> GLSL transpiler built in:

docs.unrealengine.com/4.27/en-US/ProgrammingAndScripting/Rendering/ShaderDevelopment/HLSLCrossCompiler

There are other HLSL transpilers: Microsoft's ShaderConductor, Unity's hlsl2glsl, Vulkan's vcc, etc.

To port your favorite Shadertoy examples back to UE, you can transpile GLSL to HLSL with ShaderTranspiler, glslcc, ShaderConductor, etc.

Disclaimer: I don't use UE or Shadertoy. In fact, this is my first exposure to GLSL/HLSL. My claims may be inaccurate.

Looking at the final shadertoy example (https://www.shadertoy.com/view/4XSXz3) I would think he just recreated each effect in shadertoy (variable and function names dont seem exported to me).

Most of the effects on the page are only a couple of lines it seems so maybe he did just rewrite them all? I do wonder why he bothered with UE material graphs if he's this proficient at shaders anyway.

I can imagine using material graphs is a much better way to experiment, iterate and progressively build up the effects than hand coding a shader. It's kind of like asking why write code in C# in Visual Studio when you can just write assembly?

Website acts as my portfolio - I'm a game developer, so that is why I use Unreal material graph. Shadertoy allows me to demonstrate ideas on live example that is animated and anybody can play with its code. For the most part HLSL(Unreal) can be translated to GLSL(Shadertoy), but that wasn't the case here. In Unreal I use my own custom flow textures, in Shadertoy it is not possible - everything has to be stored in code. Even though the basic idea behind Unreal and Shadertoy shaders was the same, the implementations were quite different. It was easier to just do everything twice, that to convert it. And yes - it took a lot of work :).