Bar shape: Underline glide

No tray - a short bar glides under the link. Keeps the strip behind it unless you choose None. Scroll down and the bar tightens up (Shrink when the page scrolls).

Try the others: Pill · Segmented · Underline glide · Dock · Neon · Tabs · Tiles · Bubbles · Brutalist · Gradient band

Set it in Content > Menus > (your navbar menu) > Behaviour > Bar shape, or for one page with [navbar bar="underline" /].