The Logo element which shows and hides the panel does so via an onClick attribute on a svg element. The parent Button element doesn't have any event handlers. This means that the user can't hide/show the panel using the keyboard.
To fix this, remove the action prop from the Logo, and the click handler from its SVG, and move the handler to the Button in devToolUI.tsx. It will also be necessary to manually set keyboard focus when the panel is shown, since the Button disappears in this case. I suggest setting focus to the "x" button in the panel itself.