Okay, I just did a test of this and it worked for me. I know it retains the series info and the watch history, but I’m not sure what else is retained or lost.
So I tested this on Cloak and Dagger. The series was in my FANTASY AND SCI-FI library which points to a folder D:\Plex Library\Series – Fantasy and Scifi.
I created a new folder D:\temp2021. I added this folder to my FANTASY AND SCI-FI library. So the library now points to 2 folders. I moved the series folder from D:\Plex Library\Series – Fantasy and Scifi to the new folder D:\temp2021 and all the metadata was retained.
I then created a new library called CLOAK AND DAGGER and added the D:\temp2021 folder. The folder was now being scanned by 2 libraries (CLOAK AND DAGGER and FANTASY AND SCI-FI). The new library showed the series Cloak and Dagger quite quickly but everything showed up as not watched. I then scanned the CLOAK AND DAGGER library again the watched history was the same in both libraries.
I then removed the D:\temp2021 folder from the FANTASY AND SCI-FI library and rescanned the library. The Cloak and Dagger series was now in the new CLOAK AND DAGGER library with its metadata and no longer existed in the FANTASY AND SCI-FI library.
I’ve done this over a year ago with my Fantasy and Sci-Fi series. All my series were previously in a single SERIES library and everything I needed to be retained was retained, so I hope this resolves your issue.
