1. When using arrow keys to navigate a menu, submenu's do not unfold. For example, in the editor, click the View, arrow down until "Select glyph/source/layer", the submenu does not show
2. When we are in a submenu, typing Escape only dismisses the submenu, but I think it should dismiss all open menus
3. When control-clicking in the editor and press Arrow down, the "Edit" submenu immediately opens, and we don't get a chance to arrow-navigate the top level context menu

In general, I think arrow left/right should go in and out of the submenu. macOS has good behavior that I think we should aim to copy.

I don't think we have deeper nested submenus, but it would be good if those would work the same as well.

@giovanniTramonto, this might interest you?