Hello Eric,
This property is valid for the deprecated DockingManager control. For the RadDock control you can use ToolCaptionButtons property:
To show all system buttons, you can use:
Greetings,
Julian Benkov
the Telerik team
Q2’11 SP1 of RadControls for WinForms is available for download (see what's new); also available is the Q3'11 Roadmap for Telerik Windows Forms controls.