husstanden/templates/layout/includes/side_nav.html

<style>
#sidenav-parent {
	display: flex;
	flex-direction: column;
	height:100%;
	min-height: 100%;
}

#sidenav {
    background-color: #506EE4;
    border-radius: 4px;

    z-index: 100;

    display: flex;
    flex-direction: column;

    max-width: 100%;
	height: 100%;
}

#sidenav div {
    display: flex;
    flex-direction: column;
}

#sidenav h4 {
	margin-top: 20px;
    color: white;
}

#sidenav a {
	color: #C5CBE2;
	line-height: 1;
}
#sidenav a:hover {
	color: white;
}

.navlist div, .navlist div > a {
    display: flex;
    flex-grow: 1;
	text-decoration: none;
}

.navlist div > a > span {
    flex-grow: 1;
}

.navlist div > a > i:last-child {
    justify-content: flex-end;
}

.navlist div > a > * {
	margin-left: 10px;
	margin-right: 10px;
}

.navlist .item {
	cursor: pointer;
	padding-top: 3px;
	padding-bottom: 3px;
}

#sidenav .flex-column .flex-column {
	margin-left: 30px;
	margin-right: 30px;
}

#sidenav .flex-column .flex-column > div {
	padding-top: 5px;
	padding-bottom: 5px;
	padding-right: 30px;
	padding-left: 30px;
}

#sidenav .flex-column .flex-column > div > a {
	display: list-item;
	list-style-type: disc;
}

.page.selected {
	background-color: #9F07C1;
	border-radius: 100px;
}

.downtab {

}

.hidden {
    display: none !important;
	overflow: hidden !important;
}
</style>
<div id="sidenav-parent">
<div class="d-flex flex-column" id="sidenav">
    <div class="top">
        <!-- Here be logo area -->
		<!-- <img alt="Logo" src="{{ url_for('static', filename='img/logo.svg') }}" height="40px"/> -->
    </div>
    <div class="navlist">
        <!-- Here be dropdown menus -->
        <div class="p-2"> <!-- Padding -->
			<div class="flex-column">
                <div> <!-- Collection -->
                    <a class="item" href="{{ url_for('dashboard') }}">
                        <i class="far fa-calendar-alt"></i><span>{{ _("Dashboard") }}</span>
                    </a>
                </div>
                <div>
                    <h4>{{ _("Economical") }}</h4>
                </div>
                <div>
                    <a class="item" href="{{ url_for('bills') }}">
                        <i class="fas fa-money-check-alt"></i><span>{{ _("Bills") }}</span>
                    </a>
                </div>
                <div>
                    <a class="item" onclick="toggleCategory(this)">
                        <i class="far fa-list-alt"></i><span>{{ _("Receipts") }}</span>
                        <i class="fas fa-chevron-right"></i>
                    </a>
                    <div class="downtab hidden">
						<div class="flex-column">
                            <div class="page">
                                <a href="{{ url_for('receipts') }}">{{ _("Receipts") }}</a>
                            </div>
                            <div class="page">
                                <a href="{{ url_for('warranties') }}">{{ _("Warranties") }}</a>
                            </div>
                        </div>
                    </div>
                </div>
                <div>
                    <h4>{{ _("Contacts") }}</h4>
                </div>
                <div>
                    <a class="item" href="{{ url_for('services') }}">
                        <i class="fas fa-tools"></i><span>{{ _("Services") }}</span>
                    </a>
                </div>
			</div>
        </div>
    </div>
</div>
</div>