Photo Library

Spill1970 wrote:

Want to merge many system photo library's together, what's the best way to do this? Thanks

You do not have "many system libraries" as it is only possible to have one at a time -

To merge libraries Use iCloud Photo Library setting each one as the system library and letting it sync completely then setting the next one - at the end you will have one system library containing everything except your projects and if you are not using high Sierra you face identifications -- Notes on Merging Photos Libraries

There are other ways to sort of merge libraries but you lost a lot with any other way

LN