CAB Enabling Kit - there is no way to show again smartpart that is already closed into RadDockWorkSpace.

Workaround:

         protected override void OnDockWindowClosing(DockWindowCancelEventArgs e)
        {
            if (!notifications[Suspend_Close] && e.NewWindow.Controls.Count > 0)
            {
                this.composer.SetActiveSmartPart(null);
                WorkspaceCancelEventArgs args = new WorkspaceCancelEventArgs(e.NewWindow.Controls[0]);
                OnSmartPartClosing(args);
                e.Cancel = args.Cancel;
                e.NewWindow.CloseAction = DockWindowCloseAction.Hide;
            }
            base.OnDockWindowClosing(e);
        }

        protected virtual void OnActivate(Control smartPart)
        {
            notifications[Suspend_Activated] = true;
            DockWindow dockWindow = GetSmartPart(smartPart);
            if (dockWindow != null && this.ActiveWindow != dockWindow)
            {
                dockWindow.Show();
                this.ActivateWindow(dockWindow);
            }

            notifications[Suspend_Activated] = false;
        }