.sidebar-nav li {
    position: relative;
    margin: 0;
    cursor: pointer;
}

.sidebar-nav ul:not(.app-sub-sidebar)>li:not(.file)::before {
    content: '';
    display: block;
    position: absolute;
    top: 11px;
    left: -12px;
    height: 6px;
    width: 6px;
    border-right: 1px solid #505d6b;
    border-bottom: 1px solid #505d6b;
    transform: rotate(-45deg);
    transition: transform 0.1s;
}

.sidebar-nav ul:not(.app-sub-sidebar)>li.open::before {
    transform: rotate(45deg);
}

.sidebar-nav ul:not(.app-sub-sidebar)>li.collapse::before {
    transform: rotate(-45deg);
}