Enable scroll on sticky navbar

Question

I´ve implemented a sticky left navbar, but the scroll is only applied to the content on the right-hand side. I´d like to enable a scroll for my sticky navbar as well.

Here is what I have up until now:

.responsive #top {
    overflow-x: visible !important
}

#top #wrap_all {
    overflow: visible !important;
}

#top .av-subnav-menu {
  margin: 0 auto;
  width: 100%;
}

#top #main {
  display: flex;
  flex-flow: column nowrap;
}

#top .sidebar_left .inner_sidebar {
 overflow-y: scroll;
}