Hey @Explora_Playa !
Welcome to the Zapier Community!
I did take a look and WordPress does offer an Updated Post trigger that you can use.
However, this will trigger on ALL updated posts, meaning if you published a post and go into to make a small correction, it will trigger as well.
If you don’t anticipate that happening, then this trigger may work for you.
However, for a more deliberate way to ensure you have no duplicates in Facebook, you were totally right in your thinking, duplicating the older WP post to be a newer draft and then publishing that might be the way to go.
Please let me know if you have any questions!