This article lists the breaking changes in the Kendo UI 2018 releases.
In the ComboBox, the
Tab key now acts as
Enter. Upon pressing
Tab, the ComboBox selects the item and, if the list popup is open, closes the popup. As a result, the highlighted item will be selected and a subsequent pressing of the
Tab key, both in a cascading ComboBox or a different element, will accurately focus the next focusable element. In this way, the focusing order is also kept.