After certain fields have been set on the edit node form and saved, I don't want the node author to change these anymore and therefore I have created a new variant with a response code "301 permanent redirect" in Page Manager.
My redirect destination is set to
And it does redirect the author to the intended node view (node_view in Page Manager).
But the reason I set this url destination is to be able to inform the user by showing a message at the top of that redirected page that says "You cannot edit this page any longer".
So how do I set such a message based on the destination in the URL?