AssetDatabase.LoadAllAssetRepresentationsAtPath

Description

Returns all sub Assets at assetPath.

This function only returns sub Assets that are visible in the Project view.
All paths are relative to the project folder, for example: "Assets/MyTextures/hello.png"

Note: Sub Assets can be added explicitly via AssetDatabase.AddObjectToAsset
Additional resources: AssetDatabase.LoadMainAssetAtPath, AssetDatabase.LoadAllAssetsAtPath, HideFlags.HideInHierarchy.

using UnityEngine;
using UnityEditor;

public class Example : MonoBehaviour
{
    [MenuItem("AssetDatabase/LoadAllAssetRepresentationsAtPath")]
    private static void PrintSubAssets()
    {
        Object[] data = AssetDatabase.LoadAllAssetRepresentationsAtPath("Assets/MySpriteTexture.png");

        Debug.Log(data.Length + " Sub Assets");

        foreach (Object o in data)
        {
            Debug.Log(o);
        }

        // outputs:
        //  4 Sub Assets
        //  MyTexture_0 (UnityEngine.Sprite)
        //  MyTexture_1 (UnityEngine.Sprite)
        //  MyTexture_2 (UnityEngine.Sprite)
        //  MyTexture_3 (UnityEngine.Sprite)
    }
}