[UE5] - Cannot make child class from AnimNode_Base

[munkybuttballs]

Hello - I am attempting to create a custom animation node.
I want to use AnimNode_Base as the parent class, but it is not listed in the new class dialog:

I can only find AnimGraphNode_Base, which is fine as I need to create that too:

This is my plugin’s build.cs:

// Copyright Epic Games, Inc. All Rights Reserved.

using UnrealBuildTool;

public class TwistBones : ModuleRules
{
	public TwistBones(ReadOnlyTargetRules Target) : base(Target)
	{
		PCHUsage = ModuleRules.PCHUsageMode.UseExplicitOrSharedPCHs;
		
		PublicIncludePaths.AddRange(
			new string[] {
				// ... add public include paths required here ...
			}
			);
				
		
		PrivateIncludePaths.AddRange(
			new string[] {
				// ... add other private include paths required here ...
			}
			);
			
		
		PublicDependencyModuleNames.AddRange(
			new string[]
			{
				"Core",
				"CoreUObject",
				"Engine"
			}
		);
			
		
		PrivateDependencyModuleNames.AddRange(
			new string[]
			{
				"CoreUObject",
				"Slate",
				"SlateCore",
				"InputCore",
				"HTTP",
				"AnimGraph",
				"BlueprintGraph",
				"UnrealEd"
			}
		);
		
		
		DynamicallyLoadedModuleNames.AddRange(
			new string[]
			{
				// ... add any modules that your module loads dynamically here ...
			}
			);
	}
}

What am I missing to get this to show up in the new class dialog?