At present, you can add PIN code to the entire account. But how to add a PIN to a single film such as some restrictive films such as horror, pornography and other films need a separate PIN how to operate?
The movies you and your wife create shouldn’t be in Plex if you’re going to be sharing.
TL:DR can’t be done as far as I know.
You place such content in a new library Section and then restrict access to that section.
How’s that going to work now that all libraries of a similar type (movies/tv shows/music) are mixed together in the new UI?
you can still sort them out.
Also, if access is restricted for someone, they won’t even show in the hub (which generates the list)
Upgrade to Plex Pass
https://support.plex.tv/articles/204232573-restricting-the-shares/