Hi,

      There is a cascading bug that we found in a scenario, where Telerik keeps adding default TabIndex of 0 which causes navigation problems, and removing it produces odd behavior with the JAWS Screen Reader in different browsers as mentioned under point 2. 

When the TabIndex is set :
1. The Radmenu adds tabindex=0 attribute to its rendered HTML and it causes some keyword navigation issues. 
Currently, the following navigation issues are noted when using Radmenu without removing the tab index attribute. The issues are present in keyboard and screen reader navigations.
• When tab key is pressed once the focus is on the entire menu and focus goes to the first menu item only on the second tab press. So tab has to be pressed twice to get focus on the first menu item. This is noted in all browsers.
• When using multiple Radmenus, the last item on the first Radmenu keeps highlighted after moving to the second menu. This issue is found in all browsers except IE11.

In order to fix the above:
The below javascript fix was applied. It removes the tabindex attribute from the menu using JS.

//Removes the tabindex attribute of RadMenu.
function RemoveRadMenuTabIndex() {
$telerik.$(".RadMenu[tabindex=0]").removeAttr("tabindex");
Sys.Application.remove_load(RemoveRadMenuTabIndex);
}
Taken from:

https://feedback.telerik.com/aspnet-ajax/1377202-unable-to-move-focus-away-from-radmenu-with-tabindex-0-when-tab-shift-tab-is-pressed

2. But now, when the JAWS screen reader is running:
That the tabindex gets removed via the above the JS Function, and hence the following problems occur when the TabIndex is not set :
- Using the screen reader with Edge browser, the submenu items are not showing (will not open at all) when using Radmenu with default render mode.
- The screen reader won't read the sub-menu items in any browser.

https://www.freedomscientific.com/Downloads/JAWS
Tested with screen reader JAWS 2018 (demo/trial version runs well in 40-minute mode).

RadMenu renders unneeded scroll button to its nested items in high DPI monitor. The problem can be reproduced with in 4K monitor (the zoom level does not matter).

Steps to reproduce:
1. Open https://demos.telerik.com/aspnet-ajax/menu/examples/overview/defaultcs.aspx?page=tables in high DPI monitor (4K)
2. Hover the Products item

Result: A scroll button is shown over the last item

Hovering over the RadMenu sub-item toggle arrow icon does not expand its sub-item.

Can be reproduced with the following configuration:



<telerik:RadMenu ID="RadMenu2" _OnClientLoad="OnClientLoad" runat="server" RenderMode="Auto" ShowToggleHandle="true">
    <Items>
        <telerik:RadMenuItem Text="Main Menu">
            <Items>
                <telerik:RadMenuItem Text="Item 1">
                    <Items>
                        <telerik:RadMenuItem Text="Sumbenu 1"></telerik:RadMenuItem>
                        <telerik:RadMenuItem Text="Sumbenu 2"></telerik:RadMenuItem>
                    </Items>
                </telerik:RadMenuItem>
                <telerik:RadMenuItem Text="Item 2">
                    <Items>
                        <telerik:RadMenuItem Text="Sumbenu 3"></telerik:RadMenuItem>
                        <telerik:RadMenuItem Text="Sumbenu 4"></telerik:RadMenuItem>
                    </Items>
                </telerik:RadMenuItem>
            </Items>
        </telerik:RadMenuItem>
    </Items>
</telerik:RadMenu>



Workaround:

                <script>
                    var menuItem = null;
     
                    function OnClientLoad(sender) {
                        $telerik.$(".rmToggle,.rmToggle *").on("mouseover", ExpandMenu);
                    }
                    function ExpandMenu() {
                        var item = $telerik.$(this).closest('.rmItem')[0]._item
                        if (!item.get_isOpen()) {
                            item.open()
                        }
                    }
                </script>

the scroll arrows do not have a proper z-index and get hidden when an item that is half-shown behind them is hovered, because this item gets a higher z-index.

attached is a video of the problem

WORKAROUND:
- set z-index to the arrows:

        .RadMenu .rmBottomArrow,
        .RadMenu .rmTopArrow {
            z-index: 31 !important;
        }

A workaround is to set <DefaultGroupSettings OffsetX="WIDTH OF THE ROOT MENU" ExpandDirection="Left" />