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?
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.