I didn't find any possibility in the documentation to manage the KendoDropDownButton popup state with anchorViewportLeave event.

Feature to add a separator in the list of the DropDownButton just like Kendo Menu: Items - Menu - Kendo UI for Angular (telerik.com)

The animate property of a PopupSettings object passed to the DropDownButton's popupSettings input, officially only supports a boolean value.

The component seems to already be working as expected if a PopupAnimation is passed to the animate property instead of boolean.

However, doing this results in a Typescript error, as this configuration is not officially supported:

Type '{ direction: string; }' is not assignable to type 'boolean | undefined'.
Type '{ direction: string; }' is not assignable to type 'true'.ngtsc(2322)

Please make this configuration part of the officially supported API of the component.

For reference download the attached project and run npm i and ng serve.