How can I clean up garbage from a Photos library?

Hi!

No, the new library is a copy of another Photos (not iPhoto) library which is also my main library that is synced to all my devices. I tried copying the new library file to an external drive, but its size remained the same.

Also, if I put the new library file in my iCloud drive, it says the file is Ineligible and it does not sync. Its current size is 4.7 Gb, so it should not be technically too large. But it's definitely too large to be on iCloud drive (or any other synced location) from the perspective of "comfortable use".

I wonder; if I open the package structure of the library file, would there be a branch containing useless items that I could delete? Sounds a bit random, but could be worth a try.

Or if I can't free the space, maybe I should just create an empty library, import the 57 photos into it, and just recreate the project.

Cheers,

Kim

Yes, and I would only dare to try messing with a copy of the library file :-).

I'll try to recap what's going on:

I am using iCloud Drive for syncing files, as well as other similar services. I have also enabled iCloud Photo Library. The goal here is to have a means to work on the same Project (a photo book) on different machines at different times. Since the Project objects are not shared through the iCloud Photo Library mechanism, the library file itself needs to be shared and synced, either on iCloud Drive or some other cloud based service. And it looks like a Photos library can't be synced on file level on iCloud Drive (hence "Ineligible"). But I could use OneDrive, Google Drive, Dropbox or something similar instead.

I have originally created the Project in my System library (therefore its contents sync to my other machines' System libraries), but when I noticed the Projects are not synced, I made a copy of my System library, and from this copy I deleted all but those photos that are included in the project. So now I have a library with just the content I need, including the Project. The only problem currently is that it takes up too much space for it to feasibly exist in a synced location.

So importing these same 57 photos to my primary library will not solve the problem (they are already there, as is the Project in question), as I will still not have access to the Project on multiple machines.

So it still feels like the best solution is to just bite the bullet, create an empty library, import the 57 photos into it and manually recreate the Project. It's a bit of work (80+ pages), but should result in the smallest possible file. I could copy/paste all text portions by having two libraries open simultaneously: the current library would be open on my MBP and the work-in-progress library on my iMac. Copy/paste text over Handoff should do the trick in this case.