How to add multiple trackballs in Xamarin.Forms Chart?

public class ChartTrackballBehaviorExt : ChartTrackballBehavior
{
}

<chart:SfChart.ChartBehaviors>
     <local:ChartTrackballBehaviorExt />
     <local:ChartTrackballBehaviorExt />
</chart:SfChart.ChartBehaviors>

protected override void OnAppearing()
{
    base.OnAppearing();
 
    Task.Run(async () =>
    {
        await ShowTrackball();
    });
}
 
async Task ShowTrackball()
{
    Task.Delay(1000).Wait();
 
    Device.BeginInvokeOnMainThread(() =>
    {
        trackballBehavior1.Show(pointX, pointY);
        trackballBehavior2.Show(pointX, pointY);
    });
}        

<chart:SfChart.ChartBehaviors>
    <local:ChartTrackballBehaviorExt ActivationMode="None" x:Name="trackballBehavior1" />
    <local:ChartTrackballBehaviorExt ActivationMode="None" x:Name="trackballBehavior2" />
</chart:SfChart.ChartBehaviors>

public class ChartTrackballBehaviorExt : ChartTrackballBehavior
{
    bool isActivated = false;
                
    protected override void OnTouchDown(float pointX, float pointY)
    {
        if (HitTest(pointX, pointY))
        {
            isActivated = true;
            base.OnTouchDown(pointX, pointY);
        }
    }
 
    protected override void OnTouchMove(float pointX, float pointY)
    {
        if (isActivated)
        {
            Show(pointX, pointY);
            base.OnTouchMove(pointX, pointY);
        }
    }
 
    protected override void OnTouchUp(float pointX, float pointY)
    {
        isActivated = false;
    }
}