Hi,

There is no out-of-the-box way to do that. However, you can do that by deriving from XamComboEditor and setting the position of the caret yourself:

public class CustomXamComboEdiotor : XamComboEditor
{
    private TextBox _textBoxPresenter;

    public override void OnApplyTemplate()
    {
        base.OnApplyTemplate();

        this._textBoxPresenter = this.GetTemplateChild("TextBoxPresenter") as TextBox;
    }

    protected override void OnSelectionChanged()
    {
        base.OnSelectionChanged();

        if (this._textBoxPresenter != null)
        {
            this.Dispatcher.BeginInvoke(new Action(() =>
            {
                this._textBoxPresenter.SelectionStart = 0;
                this._textBoxPresenter.SelectionLength = 0;
            }));
        }
    }
}

HTH