Multi pages post thumbnail pagination

The code has to go somewhere, either your own plugin or your own child theme. If you mean using post featured images as navigation icons, then yes, you could include such code in one of the mentioned elements. You’d need to write your own navigation function or hook into the default one, substituting the featured image for the link text.

If you meant something else by post thumbnail, the possibility is still there for your own code. You just need to know how to develop it 🙂