Great idea!

We're in the midst of completely rewriting the markup and will definitely incorporate this approach. One concern is the JS-based sizing of the navigation pane: it's a little brittle and could perhaps be achieved in CSS.

The reason of the JS-based sizing is that I didn’t want go change the normal version in same commit. So this change only adds responsiveness and removes the old select-based menu.

With some refactoring of the whole menu and use of flexbox it could be possible to remove the JS bits.

Also, we have been using the JS-based approach and tested with variety of devices. The JS-parts only run on mobile, and it’s pretty standard way to do fixed scrollable menus (allthough it’s ”legacy way”, due to nowadays flexbox and vw/vh units being available).