codes/reactstrap-demo/scss/core/_aside.scss
.aside-menu {
  z-index: $zindex-sticky - 1;
  width: $aside-menu-width;
  color: $aside-menu-color;
  background: $aside-menu-bg;
  @include borders($aside-menu-borders);

  .nav-tabs {
    border-color: $border-color;
    .nav-link {
      padding: $aside-menu-nav-padding-y $aside-menu-nav-padding-x;
      color: $body-color;
      border-top: 0;
      &.active {
        color: $brand-primary;
        border-right-color: $border-color;
        border-left-color: $border-color;
      }
    }
    .nav-item:first-child {
      .nav-link {
        border-left: 0;
      }
    }
  }

  .tab-content {
    position: relative;
    overflow-x: hidden;
    overflow-y: auto;
    border: 0;
    border-top: 1px solid $border-color;
    -ms-overflow-style: -ms-autohiding-scrollbar;

    &::-webkit-scrollbar {
      width: 10px;
      margin-left: -10px;
      -webkit-appearance: none;
    }

    // &::-webkit-scrollbar-button {    }

    &::-webkit-scrollbar-track {
      background-color: lighten($aside-menu-bg, 5%);
      border-right: 1px solid darken($aside-menu-bg, 5%);
      border-left: 1px solid darken($aside-menu-bg, 5%);
    }

    // &::-webkit-scrollbar-track-piece {    }

    &::-webkit-scrollbar-thumb {
      height: 50px;
      background-color: darken($aside-menu-bg, 10%);
      background-clip: content-box;
      border-color: transparent;
      border-style: solid;
      border-width: 1px 2px;
    }

    .tab-pane {
      padding: 0;
    }
  }
}
