uneasiness, nervousness, level
踧 centers on a state of inner disturbance: uneasiness or nervousness. The meaning "level" is likely a separate, rare sense, possibly related to stepping evenly, but the primary idea is emotional discomfort.
踧 combines 足 (foot) with 叔, which likely contributes the sound. The exact historical development is uncertain, but the character may have originally described a hesitant or uneasy stepping motion.
The foot radical 足 suggests movement, and 叔 looks like a person picking something up with a hand (又) over a small object (小). Imagine someone nervously shuffling their feet while trying to pick up a tiny item, creating a sense of uneasiness.
For シュク, imagine a nervous person shaking a shoe: "shoe-ku" -> シュク. The shoe ties to the foot radical, and the shaking captures the uneasiness.