Currency not listed

You can add any additional currency like below.
Use appropriate currency related details like name, symbol, true symbol.
Refer to https://wp-events-plugin.com/tutorials/how-to-safely-add-php-code-to-wordpress/ add this code.

function my_em_get_currencies( $currencies ){
    $currency_id = 'XXX';
    if( empty($currencies->names[$currency_id]) ) {
        $currencies->names[$currency_id] = 'xxxx';
        $currencies->symbols[$currency_id] = 'CCCC';
        $currencies->true_symbols[$currency_id] = 'ZZZZ';
    }
    return $currencies;
}
add_filter('em_get_currencies', 'my_em_get_currencies');