Such a functionality needs to be defined on an application level. In the 2018 R2 release we have added Recently Used Menu items in the Visual Style Builder application and the approach there can serve as an example.

Th attached gif file illustrates the desired behavior which is supported in the MS MenuStrip. 

Introduce menu merge when the MDI children are in RadDock

Improve the extensibility of RadMenuItem to allow easy layout modifications.

Example: http://www.telerik.com/help/aspnet-ajax/menu-items-xml.html

Examples: http://www.telerik.com/help/aspnet-ajax/menu-data-binding-overview.html

RadMenuItem should be able to be as wide  as the Image in it, if there is not text.

Currently RadMenu wraps its items when there is no enough space in the parent container. A possible alternative would be to implement scrolling.

For RadMenu there should be a property which determines whether the accelerator keys are underlined even when the RadMenu is not focused. The available options for that menu should be Yes, No and WindowsDefined

Add functionality (DropDownNeeded event for example) for load on demand for child menu items in RadMenu.

Provide information about the clicked control in the arguments of RadContextMenu DropDownOpening/ed event. This will help easily determine which control is clicked in case the same RadContextMenu is associated with more than one control.

Add text to separator items

Currently RadMenu and its drop down menus does not behave correctly when used in right to left mode.

ADD. RadMenu - add ability to replace the default drop down of the component

Problem
A typical usability problem with menus I frequently see is a menu or sub-menu (grouping of menu items beneath another menu) that instantly disappears if the user mouses over the wrong pixel while trying to mouse over to the menu item.  This can be frustrating causing the user to have to retrace their steps to once again reveal the menu and this time carefully tip-toe the mouse back through the narrow parameters allowed them so as not to trip the code just waiting to remove their destination.

Solution
This is a fairly simple problem technically which requires the library author to allow from some time delay before hiding the menu.

This feature request concerns adding a Right to left support (RTL) in RadMenu.

Menu items should stretch to fill the available area.

Automatically display scrollbars when total menu item height exceeds the available screen area.