Glass also allows its client to set a native menu bar on MS Windows platform in which case the workaround is disabled to allow activating the native menu bar when pressing F10 or ALT. Adding an empty native menu to a window won't be noticeable visually, however, Glass will still consider that this is a non-NULL menu, and hence disable the workaround.
It appears that Quantum sets a native menu for all windows unconditionally (see WindowStage.java and calls to setMenuBar()). This makes the workaround implemented at Glass turned off, and as such navigating of FX menus with keyboard doesn't work properly. To reproduce run the HelloMenu toy on MS Windows, press F10 or ALT and then press ArrowDown key. If the system menu pops up, the bug is reproduced.
To fix this issue, Quantum shouldn't set a native menu bars when it is not needed. In fact the native menu needs only be set on the Mac OS X platform.
JDK-8119274 KeyEvents like right, left arrow are not received by event filter call back on Windows only.