How to style inner elements of a composite added as menu-bar item

According to https://vaadin.com/components/vaadin-menu-bar/java-examples/items it is possible to add a component as a menu-item. If the added component is an instance of Composite with other inner elements, it is not possible to style them. As i understand this is because of the limitation of ::slotted-pseudo which does not allow selectors like .outer > .inner . Does anybody have an idea to solve this?