Proxy materialForRendering properties for Timeline animation

AnimateMaskableGraphic.cs

using System.Collections;
using UnityEngine;
using UnityEngine.UI;

[ExecuteInEditMode]
public class AnimateMaskableGraphic : MonoBehaviour {

    private Material m_Material;

    [Range(0f, 1f)]
    public float maskWipeControl;

    void Awake()
    {
        // Cache a reference to object's material.
        m_Material = GetComponent<MaskableGraphic>().materialForRendering;
    }

    IEnumerator AnimateProperties()
    {
        while (true)
        {
            // add other properties as needed
            m_Material.SetFloat("_MaskWipeControl", maskWipeControl);
            yield return new WaitForEndOfFrame();
        }
    }

    void Start()
    {
        StartCoroutine(AnimateProperties());
    }
}