The small arrows marking subsections of the panel menus always point to the
right. It seems to be OK for some cases, but what if the gnome-foot button
is plced on the right-edge panel? If the user is left-handed?

When the menus pop-up from the right screen edge, their sub-menus are
opened _to the left_ while all arrows continue to show "right". It feels
very wrong and reduces viable panel placement choices by quarter.

I suggest mirroring the arrows when a submenu has to appear on the left 


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