private_dependencies.cs

using UnityEngine;
using UnityEngine.UI;

public class ShowNumberOfCanvasChildren : MonoBehaviour
{
    [SerializeField] private GameObject _canvas;
    [SerializeField] private Text _numChildrenText;

    private void Update()
    {
        _numChildrenText.text = "Canvas child count: " + _canvas.transform.childCount;
    }
}