Hi info100123,

I've already asked developers this question and I'm waiting for the response from them.  I'll update the topic once I get some news for you.

You can do it with a code snippet in your theme functions file (or better yet run through the snippets plugin)
Change the "|" separator to the one you prefer.

add_filter( 'document_title_separator', 'wpf_document_title_separator' );
function wpf_document_title_separator( $sep ) {

    $sep = "|";

    return $sep;

}

I would like to add here that the so-called "SEO" separator (-| or whatever) is an old SEO myth. There is no reason to do that.