How to rotate the arrow of drop-down menu in the navbar on click?

[jpmvferreira]

Description

When writing a website in Quarto, whenever you have an entry on the nav-bar which has sub-entries, a drop-down menu is created that looks something like this:

My expectation is that the arrow should initially be pointing towards the right, and on press, it should rotate to point downwards, to signal an entry closed or open respectively.
However, when I click on "Talks", nothing happens, and the arrow remains that same, always pointing down.

Is it possible to achieve this behavior?

[mcanouil]

Yes, using CSS (or JavaScript).
You can find plenty of examples of this on the internet you can adapt and use.