ApplicationTitleDescriptor.title

Description

Setting this field will set the complete editor title without using any of the other fields of ApplicationTitleDescriptor.

using UnityEditor;
using UnityEngine;

public class WindowTitleExample
{
    private static void CustomTitleBar(ApplicationTitleDescriptor desc)
    {
        desc.title = $"My Editor Custom Title version: {Random.value}";
    }

    [MenuItem("Test/Setup custom title bar")]
    static void Setup()
    {
        EditorApplication.updateMainWindowTitle -= CustomTitleBar;
        // This callback will be triggered when a new scene is loaded or when Unity starts.
        EditorApplication.updateMainWindowTitle += CustomTitleBar;
        EditorApplication.UpdateMainWindowTitle();
    }
}