When DockSite.ToolWindowsTabStripPlacement is set to "Top" title bar border is still visible on the top of ToolWindowContainer. After digging into ToolWindowContainer style I dound that it has Border element with name titleBarBorder for which is set Margin property to Value="0,0,0,-1" when TabStripPlacement is Top.
<Trigger Property="TabStripPlacement" Value="Top">
<Setter TargetName="titleBarBorder" Property="Margin" Value="0,0,0,-1" />
If I manually set Margin to 0 in Snoop tool then the border disappears. Is there setting/property can help me hide title bar?