The xamDockManager™ control allows your end user to close a pane and hide it from view. However, unlike pinning and unpinning panes, there is no way for your end user to display a closed pane unless you implement functionality to open a closed pane.
When your end user closes a pane, it is hidden by default. For the default case, you need to set the content pane’s Visibility property to Visible to open the closed pane. However, if you explicitly set a content pane’s CloseAction property to RemovePane, xamDockManager removes the content pane from the docking layout. In order to open a removed pane, you have to re-add it to the proper split pane’s Panes collection or tab group pane’s Items collection.