docs/manual/source/stylesheets/partials/nav/_main.css.scss

#nav-main {
  border-right: 1px solid $border-color;
  box-sizing: border-box;
  width: 300px;
  position: fixed;
  left: 0;
  overflow: auto;
  bottom: 0;
  top: 90px;
  background-color: $nav-main-background-color;
  ul {
    padding: 0;
    margin: 0;
    display: inline-block;
    width: 100%;
    list-style-type: none;
  }
  a {
    color: $nav-main-link-color;
    box-sizing: border-box;
    display: table;
    &:hover {
      text-decoration: none;
      background-color: $nav-main-hover-background-color;
      color: $nav-main-hover-link-color;
      border-color: $nav-main-hover-background-color;
    }
    i.fa {
      display: inline-block;
      display: table-cell;
      width: 1em;
    }

    span {
      display: table-cell;
    }
  }

  & > ul {
    // Level 1
    margin-bottom: 50px;
    & > li {
      background-color: $nav-main-level-1-background-color;
      & > a {
        border-bottom: 1px solid $border-color;
        min-height: 50px;
        display: block;
        font-size: 16px;
        font-weight: 400;

        color: $nav-main-level-1-font-color;
        padding: 14px 0 10px 25px;

      }
      // Level 2
      ul {
        display: none;
        border: none;
      }

      &.expand {
        ul {
          display: block;
        }
      }

      li {
        background-color: $nav-main-level-2-background-color;

        & > a {
          min-height: 40px;
          font-size: 14px;
          display: block;
          padding: 8px 0 8px 35px;
          line-height: 20px;
          border-left: 5px solid $nav-main-level-2-background-color;
          &.active {
            background-color: $nav-main-level-2-active-background-color;
            border-left: 5px solid $nav-main-level-2-active-border-color;
            color: $nav-main-level-2-active-link-color;
            &:hover {
              color: $nav-main-level-2-active-link-color;

            }
          }
        }
      }

      // Level 3
      ul ul {
        a {
          padding-left: 55px;
        }
      }

      // Level 4
      ul ul ul {
        a {
          padding-left: 75px;
        }
      }
    }
  }
}