Print the VisualElement hierarchy with debug info. Use this with a diff tool to see what changed.

DebugHierarchy.cs

public static class DebugHierarchy
{
    public static string HierarchyToString(VisualElement root)
    {
        var sb = new StringBuilder();
        HierarchyToStringRecursive(root, sb, 0);
        var s = sb.ToString();
        EditorGUIUtility.systemCopyBuffer = s;
        return s;
    }

    static void HierarchyToStringRecursive(VisualElement root, StringBuilder sb, int depth)
    {
        ElementToString(root, sb, depth);
        depth++;

        for (int i = 0; i < root.hierarchy.childCount; i++)
        {
            var child = root.hierarchy[i];
            HierarchyToStringRecursive(child, sb, depth);
        }
    }
    
    static void PrintAllStyles(VisualElement element, StringBuilder sb)
    {
        element.resolvedStyle.GetType().GetProperties().ToList().ForEach(p =>
        {
            sb.AppendFormat("{0}: {1} ", p.Name, p.GetValue(element.resolvedStyle));
        });
    }

    static void ElementToString(VisualElement element, StringBuilder sb, int depth)
    {
        for (int i = 0; i < depth; i++)
            sb.Append("  ");

        sb.Append($"{element.GetType().Name}({element.name}) ");
        sb.AppendFormat("{0} ", element.boundingBox);
        sb.AppendFormat("{0} ", element.worldBoundingBox);
        sb.AppendFormat("{0} ", element.layout);
        sb.Append("\n");
    }
}