Going a bit nutty here, using i3 WM on top of Gnome, and am only able to trigger message tray (i.e. notification menu) display via mouse click.
On Gnome IRC I was told that there are no keybinding hooks in the notification-daemon code, therefore toggle show/hide message is not possible without a mouse click.
And yet, I can mouse click the message tray icon itself to show/hide, so there "must" be a way to simulate this mouse click event.
Thanks for any clues as to how to pull this off; otherwise, it's Dunst or other vanilla events menu, which would be ridiculous, pull entire gnome stack via default Fedora install and not be able to use notifications that work perfectly fine on mouse click ;-(