.menu-collapsed-mode li[data-top-menu-id="top_menu_id_library"] .menu-item-icon {
    background-image: url("/bitrix/css/ithive.library/img/icon-menu.svg");
    font-size: 0;
}
.bitrix24-default-theme .menu-collapsed-mode li[data-top-menu-id="top_menu_id_library"] .menu-item-icon {
    background-image: url("/bitrix/css/ithive.library/img/icon-menu-dark.svg");
    font-size: 0;
}