For V8.4.0 (I use 8.4.5) you need to add the compatibility pack, e. g. ```

Directory DragDropLayouts
1

For V8.4.0 (I use 8.4.5) you need to add the compatibility pack, e. g.

        <dependency>
            <groupId>com.vaadin</groupId>
            <artifactId>vaadin-compatibility-client</artifactId>
            <version>8.4.5</version>
        </dependency>