Add a tooltip to Menu Item

How can i add a Tooltip to menu bar?

You can use the [Element API]
(https://vaadin.com/docs/v14/flow/element-api/tutorial-properties-attributes.html) to set the HTML title attribute.

		MenuBar menuBar = new MenuBar();
		MenuItem item = menuBar.addItem("Custom Menu");
		item.getElement().setAttribute("title", "Custom Tooltip");

is it possible to edit the style of Html title attribute?

Tamar Noiman:
is it possible to edit the style of Html title attribute?

No.
You can’t style an title attribute.