Calling TreeView's CheckItem method when the control is loaded, so that you mimic a "pre-checked" TreeView results in NullReferenceException in RadTreeView.Checkbox ToggleItem method.
When CollapseAll method is called, if the first element is out of the screen (after a scroll), the treeview crashes. Available in minor release 2018.3.1109. It will also be available in the R1 2019 release.
Available in R3 2018 release.
Expose a BringIntoView or ScrollIntoView method that would scroll the TreeView to a specified TreeViewItem. Available in R3 2018 release. For more details on the feature refer to: https://docs.telerik.com/devtools/xamarin/controls/treeview/treeview-scrolling