Creating a shared iCloud Photo Library for duplicate photos

Once you have sent photos to an album, you still have a duplicate photo in your main library. I read somewhere on the community that you can create a "shared icloud photo library for yourself", where you can then hide these dublicate photos from your main Library, that are already saved in an album. Does anyone actually know how to create a shared icloud photo library for yourself and then put your duplicate photos in it? I just really want to get rid of the duplicates in my main library, without deleting them in the album.

thank you very much

[Re-Titled by Moderator]