Setting the Hover Effect 
The hover effect allows users to mouse over a first-level tab in top-level navigation to see the tab's second level entries. This function is activated by setting a specific property of the Top-Level Navigation iView (com.sap.portal.topLevelNavigationiView).
In the Portal Catalog, go to .
Right-click Classic Framework Page (com.sap.portal.frameworkpage) and choose to display the page in the Page Editor.
Select the Top-Level Navigation iView and click Properties to display the iView's properties in the Property Editor.
From the Property Category dropdown list, select Show All.
Browse to the Hovering property and enter the value True.
Click Save.
Note
The hover feature must be disabled in the following cases:
In portals whose Accessibility flag is enabled.
In desktops used for navigation zoom windows.
More information: Configuring Navigation Zoom