Hi Kien,
Thank you for using Syncfusion products.
We have checked the reported query “How to customize the Scrollbar of SfListView’ from our side. We would like to inform you that we have used Xamarin.Forms ScrollView for interaction purpose in SfListView, and there are no customization options for ScrollView’s ScrollBar.
Meanwhile, you may try to load the ScrollView outside the ListView and set the IsScrollingEnabled property as false and implement the following custom renderer for ScrollView in the sample level,
Reference links:
Please let us know if you need further assistance.
Lakshmi Natarajan