high and flat, broad, spacious
敞 centers on openness and expansive flatness: a broad, spacious area that is high and unobstructed.
敞 combines 尚 (high, esteemed) with 攵 (strike/action), suggesting an action that makes something high and open. The exact historical development is uncertain.
The left side 尚 suggests something elevated, and the right side 攵 looks like an action. Imagine striking open a high, flat plain to create a broad, spacious area.
For ショウ, picture a show being performed on a high, flat stage: show -> ショウ, and the stage is broad and spacious.