Version: 2018.1
public static List<Selectable> allSelectables ;

Description

List of all the selectable objects currently active in the scene.

UI.Selectable.allSelectables.

using UnityEngine;
using System.Collections;
using UnityEngine.UI; // required when using UI elements in scripts

public class Example : MonoBehaviour { //Displays the names of all selectable elements in the scene public void GetNames() { foreach (Selectable selectableUI in Selectable.allSelectables) { Debug.Log(selectableUI.name); } } }