An example of Unity Shader Graph Custom Node's designed and developed on World of Zero: https://youtu.be/FeL4uWGdtUY

CustomNode.cs

// Custom Shader Graph Node for Unity
// Developed for World of Zero: https://youtu.be/FeL4uWGdtUY
// Based on examples from: https://github.com/Unity-Technologies/ShaderGraph/wiki/Custom-Nodes-With-CodeFunctionNode

using UnityEngine;
using UnityEditor.ShaderGraph;
using System.Reflection;

// The Title is a list of menu's and submenu's that will define where this node is placed in Unity's Shader Graph UI
[Title("Custom", "Binary Select (Menu)")]
public class CustomNode : CodeFunctionNode {
	
	public CustomNode() {
    // Define the name of the node (this is shown on existing nodes)
		name = "Binary Select";
	}

    protected override MethodInfo GetFunctionToConvert()
    {
        // Use Reflection to find the BinarySelectFunction below to pass it to Unity's API
        // The use of "BinarySelectFunction" here can be swapped for nameof(BinarySelectFunction) in higher versions of .NET
       	return GetType().GetMethod("BinarySelectFunction",
			BindingFlags.Static | BindingFlags.NonPublic);
    }

  // Define a static function that returns the generated shader code based on the set of predefined inputs and outputs.
	static string BinarySelectFunction(
		[Slot(0, Binding.None)] Vector1 Input,
		[Slot(1, Binding.None)] DynamicDimensionVector Result0,
		[Slot(2, Binding.None)] DynamicDimensionVector Result1,
		[Slot(3, Binding.None)] out DynamicDimensionVector Out
	)
	{
    // Takes advantage of C#'s verbatim string feature to preserve whitespace and newlines.
		return @"
{
	Out = ((1 - Input) * Result0) + (Input * Result1);
}
";
	}
}