dejected, dispirited, vague, faint, grand
惝 centers on a mental state of emptiness or loss: feeling dejected, dispirited, or vague. The sense of 'grand' may be a rare or archaic extension, but the core idea is a hollow, faint emotional state.
惝 combines the heart radical 忄 with 尚, which likely contributes a phonetic element. The exact historical development is uncertain, and the character is rare in modern Japanese.
The heart radical 忄 beside 尚 suggests a heart that is merely 'still' or 'yet'—emotionally suspended, leading to feelings of dejection and vagueness.
For ショウ, imagine a dejected person giving a faint 'show' of emotion: show -> ショウ, but the heart is too dispirited to put on a real performance.