Hit the Super key. This brings up the menu in the upper left. "All" is highlighted. Logically, pushing the down arrow would scroll down to the next item on the left panel. (Actually, there is a blinking cursor in the search dialog at the same time that "All" is highlighted, which is doubly confusing.) But it doesn't. It scrolls to the next item in the right panel. Normally, I would expect to need to hit Enter first in order to select the submenu for "All". Then if I wanted exit back out of the submenu, I would hit "Esc". I can't figure out how to scroll down the left menu, for example to "Graphics", without using the mouse, which is awkward or sometimes impossible when the touchpad stops working.
Just a quick comment, as I am experiencing slightly different behavior:
First, I would note that when using the arrow keys, I can, in fact, navigate the menu, but the highlight for the menu object which is currently in focus is very slight ... just a faint dotted box and not at all similar to the way that the "All" menu entry is highlighted. Hitting enter will launch the item that has focus.
I would also note that while the LHS Super key reliably launches the menu, it does not reliably close the menu. Perhaps one out of seven attempts will successfully toggle the menu closed, while the Esc key does, in fact, reliably close the menu. The menu does not react at all to my RHS Super key.