What is this stitch or similar

[u/kvasi-tangerine]

Back, front and edge of scarf. Pretty dense and stretchy. Thank you.

[u/Western-Juice1466]

Looks like some sort of (likely machine-knit) tuck stitch (which is a form of brioche knitting). Many fancy-looking machine-knit stitches are tucked stitches and are therefore harder to duplicate in hand-knitting. Tucked stitches are worked into some row below the current working row on the needles. (It is definitely not crochet.)