flatsome-theme-customize-accounts-area.php

<?php
//flatsome theme customize accounts area

function add_flatsome_account_links() {

$label = "My Test Link";
$endpoint = "test-endpoint";
?>
<li class="<?php echo wc_get_account_menu_item_classes( $endpoint ); ?>">
      <a style="color: red" href="<?php echo esc_url( wc_get_account_endpoint_url( $endpoint ) ); ?>"><?php echo esc_html( $label ); ?></a>
    </li>

<?php
}
add_filter('flatsome_account_links','add_flatsome_account_links');