Simple Unity script to create a scrolling marquee.

Marquee.cs

using UnityEngine;

public class Marquee : MonoBehaviour
{
    public string message = "Where we're going, we don't need roads.";
    public float scrollSpeed = 50;
    
    Rect messageRect;
    
    void OnGUI ()
    {
        // Set up message's rect if we haven't already.
        if (messageRect.width == 0) {
            var dimensions = GUI.skin.label.CalcSize(new GUIContent(message));
            
            // Start message past the left side of the screen.
            messageRect.x = -dimensions.x;
            messageRect.width = dimensions.x;
            messageRect.height = dimensions.y;
        }
        
        messageRect.x += Time.deltaTime * scrollSpeed;
        
        // If message has moved past the right side, move it back to the left.
        if (messageRect.x > Screen.width) {
            messageRect.x = -messageRect.width;
        }
        
        GUI.Label(messageRect, message);
    }
}

Thank you!

I've recently run into this and with the new UIDocuments the above method didn't work well for me. This was my fix. Hope it helps someone.

    private IMGUIContainer container;
    private const float scroll_speed = 0.001f;

    private void OnEnable()
    {
        container = GetComponent<UIDocument>().rootVisualElement.Q<IMGUIContainer>("footer");
        StartCoroutine(AutoScroll());
    }
    private IEnumerator AutoScroll()
    {
        float position = 100f;
        while (position >= -100f)
        {
            container.style.left = Length.Percent(position);
            position = (position <= -9f) ? 100f : position -= 0.01f;
            yield return new WaitForSeconds(scroll_speed);
        }
    }

from there you can do stuff like container.Add(message_label); assuming Label message_label;