When direct sun causes screen visibility issues, it's because you're seeing the sun's reflection in the screen. Because you're usually standing directly above the screen, that means that your head is right between the sun and the screen. Any shade that would block the sun would also block your view of the screen. The only fix is to be under a canopy, or to play when the sun is at a steeper angle.
The mini-display tuner mode is a real help here. Or an FC-6, whose main display shows the current preset, scene and tuner. FC-6 main screen don't care about no direct sun.