How to add a new language that is not in WordPress dropdown?

If you want to add a new language that is not in WordPress dropdown or copy an existing one with a new name please proceed as indicated below:

Go to cPanel/ FTP > File Manager > public_html > wp-content > themes > wpjobster-child > edit 'functions.php' an add below mentioned code > Save changes

add_filter( 'wpj_languages_list_filter', 'my_new_languages', 10, 1 );
function my_new_languages( $language_codes ) {
    $language_codes['mnl'] = __( 'My new language', 'wpjobster-child' );
    return $language_codes;
}

On the third line please change in between comas the text 'My new language' with the name of your language and 'mnl' with the slug of your language