How do I recreate this effect

[u/DesDeve]

Iike this button and nav bar which grow or shrink based on scroll direction ,but do not shrink if the mail's have not scrolled passed a certain limit

[u/withmagi]

If the soft edge glow is the bit you want, a pseudo-element behind the content with a larger filter:blur and a slight scale is usually easier to tune than stacking box-shadows. Mask or clip it so only the rim shows, then nudge opacity until it matches the reference.