How to get a reference to a prefab asset in unity

I have the following class

    using System.Collections;
    using System.Collections.Generic;
    using UnityEngine;
    
    public class PixelSystem
    {
        public GameObject pixelPrefab;
        public Texture2D[] style;
        public List<Chunk> chunks;
        public GameObject mGameObject;
        public PixelSystem(GameObject _mGameObject)
        {
            mGameObject = _mGameObject;
            chunks = new List<Chunk>();
        }
    }

Chunk and Pixel are structs but I don't think they are relevant.

I would like pixelPrefab and style to be serialized but cannot seem to be able to make that work. This script is not attatched to a GameObject.

I have looked into getting the assets at runtime with Resources or Addressables but I would like to be able to set these fields from the editor.

I have tried making the class inherit from MonoBehaviour and having [SerializeField] public GameObject pixelPrefab; and [SerializeField] public Texture2D[] style;, but the result of this is that pixelPrefab is settable from the editor but instead of showing style it shows mGameObject, for some reason... ¯\_(ツ)_/¯ Edit: Turns out that the [SerializeFields] do nothing here, the result is the same without them.

I've also tried puting [System.Serializable] before the class, but as far as I can tell this does nothing at all.

Someone plz help.

Edit:

Due to some misunerstandings I would like to clarify a few things:

1. I have the prefab asset already, it is in my assets folder not in my scene, creating the assets is not the problem.
2. pixelPrefab would work fine as a static property, however, style would not.
3. Style only needs serializing for a default value and so is not a priority.
4. This code is very incomplete, the constructor is incomplete, I want an answer to this qusetion before I spend time writing code that may be unusable.
5. I want to select the assets in the editior
6. I do not want to have a function that must be called before the classes are used, so that the assets are loaded
7. I do not want to load the assets each time they are referenced, so no get {load();}

This is what I want to see in the editor when I select my script:

And this is the closest thing to what I want so far:

Which I get by setting the class to inherit from MonoBehaviour, I'd rather not inherit from anything, and idk if you are meant to have MonoBehaviour classes that aren't attatched to gameObjects, but if this is necessary then so be it.

complete .cs file here

A few things here. I'm going to assume this point is the most important:

5. I want to select the assets in the editior

So, in order to be able to do this, every field you want to see has to be able to be serialized by Unity and also Unity needs to be able to draw the GUI for that thing. You said,

I would like pixelPrefab and style to be serialized but cannot seem to be able to make that work.

and again here I'm taking "serialized" to really mean that you just want those fields exposed in the Editor so you can stick things into them. So when you give me the following snippet I immediately see several issues:

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class PixelSystem
{
    public GameObject pixelPrefab;
    public Texture2D[] style;
    public List<Chunk> chunks;
    public GameObject mGameObject;
    public PixelSystem(GameObject _mGameObject)
    {
        mGameObject = _mGameObject;
        chunks = new List<Chunk>();
    }
}

The first is that PixelSystem itself isn't serialized. You either need to tag the class with [System.Serializable] to use Unity's serializer or you need to inherit from something that Unity already knows should be serialized, like Component or MonoBehaviour (MonoBehaviour inherits Component). The issue with Component and subclasses is that they need to exist on a GameObject, so you can't new a Component, you have to .AddComponent<YourComponent>().

Now as you've discovered, when you have your script inherit MonoBehaviour, you see

that pixelPrefab is settable from the editor but instead of showing style it shows mGameObject, for some reason... ¯\_(ツ)_/¯

And the reason it's showing mGameObject can be seen in your class' member variables:

public GameObject pixelPrefab;
public Texture2D[] style;
public List<Chunk> chunks;
public GameObject mGameObject;

You can see that pixelPrefab is a public GameObject. Great! (1) your class is inheriting MonoBehaviour, so Unity knows to serialize it, (2) pixelPrefab is public, so the Editor knows to show it, and GameObject is itself a serializable object that Unity knows how to draw, so the end result is that Unity adds pixelPrefab to the Editor GUI for your class.

Then you get to style, which is public, so the Editor knows it should show it, but it's an array and Unity doesn't know how to draw the Editor GUI for an array. It's an array of Texture2D, which it does know how to draw, but it doesn't know how to handle the array aspect, so it doesn't add style to your GUI.

Then you get to chunks, which is public, so the Editor knows it should show it, and it's a List, which Unity does know how to handle, but it's a List of Chunk, which I'm betting is not inheriting MonoBehaviour and is also not tagged with [System.Serializable], so Unity doesn't know that it's supposed to be serializing Chunk. This means that it does know it's supposed to be drawing a list, but it think it's not supposed to be drawing any contents for the list, so it skips the list completely.

Finally you get to public GameObject mGameObject, which gets drawn for all the same reasons that pixelPrefab gets drawn, and finally you get what you see in the Editor in your last screenshot: Only pixelPrefab and mGameObject are drawn in your class GUI:

So, what to do if you want to view your class in an Editor pane and you also want to see pixelPrefab and style?

1. Have something that can be serialized, like a MonoBehavior, hold a reference to PixelSystem OR have PixelSystem inherit MonoBehavior.
2. If PixelSystem is not a MonoBehavior then it needs to have [System.Serializable] on the line above public class PixelSystem.
3. Do what you've already done and have public GameObject pixelPrefab.
4. Convert style from an array to a list so Unity knows how to draw it.

You should wind up with the following:

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

[System.Serializable]    
public class PixelSystem
{
    public GameObject pixelPrefab;
    public List<Texture2D> style = new List<Texture2D>();
    public List<Chunk> chunks;
    public GameObject mGameObject;
    public PixelSystem(GameObject _mGameObject)
    {
        mGameObject = _mGameObject;
        chunks = new List<Chunk>();
    }
}

You can also have Chunk be serialized and shown in your Editor pane if you tag that class with [System.Serializable], and you only need the [SerializeField] tag for fields that aren't already public. You can still add that tag to public fields just like you can add [System.Serializable] to a MonoBehaviour but it's redundant. Not required.