How do I make a widget be visible only when another is hovered?

[RubenVerg]

I'm trying to make a widget appear on hovering another component; I would like for the hoverable component to be in a zstack with the hover result, but even putting them next to each other in a vstack doesn't seem to work. Here's what I thought would work:

buildUI wenv model = let
  b = label "hover me" `styleBasic` [border 2 green] `styleHover` [border 2 red]
  h = label "hovered!" `styleBasic` [border 2 blue] `nodeVisible` isNodeHovered wenv b
  in vstack [b, h]

When I hover on b, nothing happens. What's the correct way to do what I want?