While Mac's can have multiple Photos Libraries, iOS, iPadOS, and iCloud can each only have one-- the same one if they are all on the same account. However, you can separate a Library into two parts-- the general idea is to have one part you can share with other accounts. But you can just share with yourself.
How to use iCloud Shared Photo Library - Apple Support
Use iCloud Shared Photo Library on iPhone – Apple Support (UK)
Honestly, I haven't done this, so I'm not sure what complications there are. But others use this all the time to separate out a set of pictures, like curated and not curated, and share just with themselves. As long as it's the creator account, you can see both.
You can try it with your current System Library, and then see if you want to add another Library. You would need to Merge Libraries, and the best way to do that is to use the trusted 3rd party app PowerPhotos ($35) which will maintain the albums and folders in a merge.
Let us know if this looks like it would work for you. I'm curious…