> I went to Options, File Types, and looked for this file extension to see if I could un-check it from being displayed but can't find it.
I can't find a way to remove them from view either.
But are you sure that you need these .TP_JPTN files at all? ThumbsPlus makes them for you when you have this option on:
Options | Preferences | Thumbnail | Create persistent .tp_jptn files for thumbnails made from clipboard
These persistent images are used to re-make thumbnails from files that can only be thumbnailed through the clipboard method. So, if you don't expect to ever re-make those thumbnails, maybe you don't need them and you can delete them.