With interactions, add a Hover event, check the “Affect different element(s)” box and type in the class given to your other and hidden element. (Then I guess, adjust the opacity to 100%)
We’re also looking at adding this natively relatively soon, so you’ll be able to achieve this with CSS without resorting to interactions. It’ll work somewhat similar to the Product Grid example on the CSS Playground: http://playground.webflow.com/ (notice the “when located in” wording in the UI). For the time being, the Custom Code and Interactions approaches could be used as a workaround. Thanks for your patience!
It’s the very old UI that was for playground. I remember it from a year ago Beside, there is nothing more than on the current one. There is even less.