odoo18/addons/account/static/src/css/account_payment.scss

.o_popover_header {
    padding: 5px 0 5px 8px;
    border-bottom: 1px solid #ccc;
}

.o_memo_content {
    max-width: 200px;
    overflow: hidden;
    text-overflow: ellipsis;
    display: -webkit-box;
    -webkit-line-clamp: 3;
    -webkit-box-orient: vertical;
}