How to get Page Manager to react on path alias before node/%node
If you want to override the default path like node/%node, taxonomy/term/%taxonomy_term and so on then there is a module for that: Page manager existing pages. Some more details about this module (from its project page):


  Page manager existing pages allows you to override/configure Drupal menu paths so you can create variants with Page manager, which is bundled in the CTools project.


Here is an introduction from the author: Overriding any Drupal path with Page manager existing pages.