Admin toolbar default left / vertical
If you go through its possible to make it as horizontal. Try this code wherever needed:

jQuery('#toolbar-bar button').each(function(){
  if(jQuery(this).html() === 'Vertical orientation'){
    jQuery(this).click();
  }
  if(jQuery(this).find('span.label').text() === 'Tools'){
    var open = jQuery(".toolbar-box").find('.open').length;
    if (open &gt; 0) {
      jQuery(this).find('span.label').click();
    }
  }
});


For checking try this in the console first and add snippet to your JS file.