Shaker/Avalonia/SukiUI.Dock/ToolContentControl.axaml

<ResourceDictionary xmlns="https://github.com/avaloniaui"
                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
  <Design.PreviewWith>
    <ToolContentControl Width="300" Height="300" />
  </Design.PreviewWith>

  <ControlTheme x:Key="{x:Type ToolContentControl}" TargetType="ToolContentControl">

    <Setter Property="Template">
      <ControlTemplate>
        <DockableControl TrackingMode="Visible">
          <ContentControl Content="{Binding}" 
                          ContentTemplate="{Binding}" />
        </DockableControl>
      </ControlTemplate>
    </Setter>

  </ControlTheme>

</ResourceDictionary>