Custom property that allows to reference scene asset directly from the Editor

public class SceneLoader : MonoBehaviour
{
    [SerializeField] private SceneReference sceneToLoad;

    private void Start()
    {
        SceneManager.LoadSceneAsync(sceneToLoad);
    }
}

The package is available on the openupm registry. It's recommended to install it via openupm-cli.

openupm add com.skibitsky.scene-reference

Open Packages/manifest.json with your favorite text editor. Add the following line to the dependencies block.

{
    "dependencies": {
        "com.skibitsky.scene-reference": "https://github.com/skibitsky/scene-reference.git"
    }
}

Notice: Unity Package Manager records the current commit to a lock entry of the manifest.json. To update to the latest version, change the hash value manually or remove the lock entry to resolve the package.

"lock": {
  "com.skibitsky.scene-reference": {
    "revision": "master",
    "hash": "..."
  }
}