VRCMelonAssistant/VRCMelonAssistant/Styles/Thumb.xaml

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
    <Style x:Key="VRCMelonAssistantThumb" TargetType="{x:Type Thumb}">
        <Setter Property="FrameworkElement.OverridesDefaultStyle" Value="True" />
        <Setter Property="IsTabStop" Value="False" />
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type Thumb}">
                    <Rectangle
                        Name="rectangle"
                        Width="{TemplateBinding Width}"
                        Height="{TemplateBinding Height}"
                        Fill="{DynamicResource ScrollBarHandle}"
                        SnapsToDevicePixels="True" />
                    <ControlTemplate.Triggers>
                        <Trigger Property="UIElement.IsMouseOver" Value="True">
                            <Setter TargetName="rectangle" Property="Fill" Value="{DynamicResource ScrollBarHandleHovered}" />
                        </Trigger>
                        <Trigger Property="Thumb.IsDragging" Value="True">
                            <Setter TargetName="rectangle" Property="Fill" Value="{DynamicResource ScrollBarHandleClick}" />
                        </Trigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
</ResourceDictionary>