I want edit_post_link() to open in a new window/tab (target=”_blank”)

You can adjust the link via the edit_post_link filter.

Here’s an example where we use a simple replace since we don’t have the class and url explicitly as input arguments:

add_filter( 'edit_post_link', function( $link, $post_id, $text )
{
    // Add the target attribute 
    if( false === strpos( $link, 'target=" ) )
        $link = str_replace( "<a ', '<a target="_blank" ', $link );

    return $link;
}, 10, 3 );