Shows how to modify the Panels display on a node.

panelizer-modify.php

$nid = 123;
$node = node_load($nid);

$display =& $node->panelizer['page_manager']->display;
foreach ($display->content as $pid => $pane) {
  if ($pane->uuid == 'd195a038-1e7d-45e7-9232-22e4c6f4da3e') {
    $display->content[$pid]->configuration['path'] = 'blerg';
  }
}

// This will trigger Panelizer to clone the default and create a custom Panel if one
// doesn't already exist.
$node->panelizer['page_manager']->display_is_modifed = TRUE;

// When this is already a custom panel, we need to save the Panel ourselves.
if ($node->panelizer['page_manager']->did) {
  panels_save_display($display);
}

node_save($node);