Lubuntu 18.04.5 and 20.04 how open start menu using key window?

I use both Lubuntu 18.04.5 and 20.04.
How configure when use the keyboard window key to open the start menu in both 18.04.5 and 20.04 ?
In Lubuntu 20.04 the system had crashed and when restarted anything had breaked the window key that not works. How fix to open the start menu ?
Thanks very much for read and your reply.

“Application Menu”: Preferences ->LXQt Settings -> Shortcut Keys

Then see attached:

Unfortunately doesn’t mention “Super_L” which is the key in question.

Oh, BTW, I’m pretty sure that there’s no option for this in 18.04. The reason this works in 20.04 is because of lxqt-globalkeys which doesn’t exist in 18.04 (which is based on LXDE not LXQt).

That leaves your other option to be OpenBox and it’s incapable, at least not without causing problems for any other shortcut using the same key: