Answer by Matthias Pfefferle for Adding two sidebars in wordpress child theme

You can add both sidebars to the sidebar.php of your childtheme and arrange them per css.

// your sidebar<div id="left-sidebar"><?php dynamic_sidebar( 'sidebar-left' ); ?></div><!--#left-sidebar-->// original sidebar<div id="sidebar"><?php dynamic_sidebar( 'sidebar' ); ?></div><!--#sidebar-->

Be sure to add both sidebars because the sidebar.php of your child theme overwrites the original one.