MainPage.xaml

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:sfinputs="clr-namespace:Syncfusion.Maui.Inputs;assembly=Syncfusion.Maui.Inputs"
             x:Class="SfComboBoxTest.MainPage">

    <Grid ColumnSpacing="5" RowDefinitions="50, 60" ColumnDefinitions="15, 160, 180" >
        <Button Grid.Row="0" Grid.Column="1" 
                Text="Rest Combo box index" Pressed="Button_Pressed"/>

        <Label Grid.Row="1" Grid.Column="1"
                Text="Select Nights To Stay" FontSize="Body" FontAttributes="Bold" LineBreakMode="WordWrap" HorizontalTextAlignment="End" VerticalOptions="Center" />

        <sfinputs:SfComboBox Grid.Row="1" Grid.Column="2"
                Placeholder="# Nights" HorizontalTextAlignment="Center" PlaceholderColor="Gray"
                FontSize="Medium" MaxDropDownHeight="190" DropDownItemHeight="35" ItemsSource="{Binding BookingAlternativeList}"  
                SelectedIndex="{Binding BookingListIndex}" MaximumWidthRequest="140" HorizontalOptions="Center" Background="Transparent" 
                Stroke="Transparent" IsClearButtonVisible="False" SelectionChanged="BookingList_SelectedIndexChanged" />

    </Grid>
</ContentPage>