Problema nel creare “Pagina di documentazione tecnica “

Ciao, sto facendo la pagina di documentazione tecnica e ho un problema, nn riesco a mettere la barra di scroll nella parte contenente la lista laterale, che ho chiuso in un div.
Ho messo nel css nella classe del div contenente la lista un overflow : auto; ma niente non so dove sbaglio. Vi mando un immagine.

Please don’t post pictures of code. Since it is in CodePen, a link to the pen would be much more helpful.

My problem is that i don’t success to put a scrollbar in my div with class=“ex1”, that includes my list elements. i ve put the key {overflow:auto} in css in my .ex1 but it doesnt work, and it doesnt work neither for the tag li exported in css.
Waiting for help

If I understand you, you want to know why your side menu does not have a vertical scrollbar. I’m no CSS wizard, but…

Scrollbars (if overflow is auto) only show up is needed. Since that div can expand to show all of its contents, there is no need. We can force the need by limiting its height:

.ex1 {
  overflow: auto;
  width: 320px;
  height: 400px;
}

If I’ve misunderstood, please clarify further.