How to Draw a list of non-MonoBehaviour Objects, that Inherits same Class in Unity Editor?

Question

I have a List<AbilityEffect> effects and a lot of sub-classes of AbilityEffect, such as DamageEffect, HealEffect e.t.c. that HAVE [System.Serializable] property on it. If I create class with field such as DamageEffect - Default editor will draw it perfectly! (And other effects too!)

I've added a ContextMenu Attribute to this function in AbilityData.cs

[ContextMenu(Add/DamageEffect)]

public static void AddDamageEffect()
{
    effects.Add(new DamageEffect());
}

BUT default Unity Editor draws it if was an AbilityEffect, NOT a DamageEffect!

I've write some Custom Editor for class, that contains List<AbilityEffect> effects = new List<AbilitiEffect>(), write code that draws a custom list! But how do I tell a Editor to draw a DamageEffect specifically, NOT AbilityEffect?

I'll put some code below:

Ability Data Class

using UnityEngine;
using System.Collections.Generic;

[CreateAssetMenu(fileName = "New Ability", menuName = "ScriptableObject/Ability")]
public class AbilityData : ScriptableObject
{
    public int cooldown = 0;
    public int range = 1;
    public List<AbilityEffect> effects = new List<AbilityEffect>();
    public bool showEffects = false;

    [ContextMenu("Add/DamageEffect")]
    public void AddDamageEffect()
    {
        effects.Add(new DamageEffect());
    }
}

Ability Data Editor Class

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

[CustomEditor(typeof(AbilityData))]
public class AbilityEditor : Editor
{
    public override void OnInspectorGUI()
    {
        var ability = (AbilityData)target;
        DrawDetails(ability);
        DrawEffects(ability);
    }

    private static void DrawEffects(AbilityData ability)
    {
        EditorGUILayout.Space();
        ability.showEffects = EditorGUILayout.Foldout(ability.showEffects, "Effects", true);

        if (ability.showEffects)
        {
            EditorGUI.indentLevel++;
            List<AbilityEffect> effects = ability.effects;
            int size = Mathf.Max(0, EditorGUILayout.IntField("Size", effects.Count));

            while (size > effects.Count)
            {
                effects.Add(null);
            }

            while (size < effects.Count)
            {
                effects.RemoveAt(effects.Count - 1);
            }

            for (int i = 0; i < effects.Count; i++)
            {
                DrawEffect(effects[i], i);
            }
            EditorGUI.indentLevel--;
        }
    }

    private static void DrawDetails(AbilityData ability)
    {
        EditorGUILayout.LabelField("Details");
        EditorGUILayout.Space();

        EditorGUILayout.BeginHorizontal();
        EditorGUILayout.LabelField("Cooldown", GUILayout.MaxWidth(60));
        ability.cooldown = EditorGUILayout.IntField(ability.cooldown);
        EditorGUILayout.LabelField("Range", GUILayout.MaxWidth(40));
        ability.range = EditorGUILayout.IntField(ability.range);
        EditorGUILayout.EndHorizontal();
    }

    private static void DrawEffect(AbilityEffect effect, int index)
    {
        //if (effect is DamageEffect)
        //    effect = EditorGUILayout
        // HOW??
    }
}

Ability Effect class (NOT ABSTRACT)

[System.Serializable]
public class AbilityEffect
{
    public virtual void Affect() { }
}

Damage Effect Class

[System.Serializable]
public class DamageEffect : AbilityEffect
{
    public int damageAmout = 1;
    public override void Affect() { ... }
}

Answer 1

Because of how Serialization works, once you deserialize some data Unity will try to populate an object instance based on the type specified in the class definition. If you have a List<AbilityEffect> Unity won't be able to differentiate which specific AbilityEffect you previously serialized. There is really one solution, change AbilityEffect to be a ScriptableObject, so that Unity doesn't actually serialize them as raw data but as GUID references, so that the referenced assets know by themselves what subtype of AbilityEffect they are. The downside is that this way all your effects will have to be assets in your Assets folder.