Hi @Mowgli, thanks for your post. It is possible to make those underline, using some custom css, but we do not have support for marking the “active” slide. This is on our Wish list: http://forum.webflow.com/t/add-a-current-or-active-class-to-the-currently-displayed-slide/5586
To put the text decoration on the slider navlinks:
<style>
.w-slider-nav.w-num>div {
text-decoration: underline;
}
</style>
Add this to the Header of your site in Custom Code from Site Settings: Custom code in head and body tags | Webflow University
Cheers,
Dave