Semi.Avalonia/demo/Semi.Avalonia.Demo/Themes/ToggleSwitch.axaml

<ResourceDictionary xmlns="https://github.com/avaloniaui" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
    <ControlTheme x:Key="ThemeToggleSwitch"
                  BasedOn="{StaticResource ButtonToggleSwitch}"
                  TargetType="ToggleSwitch">
        <Setter Property="Padding" Value="8" />
        <Setter Property="OnContent" Value="{Binding $self.Content}" />
        <Setter Property="OnContentTemplate">
            <DataTemplate>
                <PathIcon Theme="{StaticResource InnerPathIcon}" Data="{Binding}" />
            </DataTemplate>
        </Setter>
        <Setter Property="OffContent" Value="{Binding $self.Content}" />
        <Setter Property="OffContentTemplate">
            <DataTemplate>
                <PathIcon Theme="{StaticResource InnerPathIcon}" Data="{Binding}" />
            </DataTemplate>
        </Setter>
        <Setter Property="ContentTemplate">
            <DataTemplate>
                <PathIcon Theme="{StaticResource InnerPathIcon}" Data="{Binding}" />
            </DataTemplate>
        </Setter>
    </ControlTheme>

    <ControlTheme x:Key="SplitViewToggleSwitch"
                  BasedOn="{StaticResource ThemeToggleSwitch}"
                  TargetType="ToggleSwitch">
        <Setter Property="Foreground" Value="{DynamicResource ButtonDefaultTertiaryForeground}" />
        <Setter Property="Content" Value="{StaticResource SemiIconSidebar}" />
    </ControlTheme>
</ResourceDictionary>