add a button to the header element of a radcollapsible panel

RadButtonElement buttonElement = new RadButtonElement()
            {
                Text = "Custom Button",
            };

this.YourCollapsiblepanelName.CollapsiblePanelElement.HeaderElement.Children.Insert(1, buttonElement);

        public RadForm1()
        {
            InitializeComponent();
            RadButtonElement buttonElement = new RadButtonElement()
            {
                Text = "Custom Button",
                MinSize= new Size(100,20),
                MaxSize = new Size(100,20),
                StretchHorizontally = false
            };

            this.radCollapsiblePanel1.CollapsiblePanelElement.HeaderElement.Children.Insert(1, buttonElement);
        }