Import photos from another library in Photos on Mac
If you organize your collections of photos in individual libraries, you can import photos from one library into another.
If the Photos app
on your Mac is open, choose Photos > Quit Photos.To reopen Photos, press and hold the Option key, then click the Photos icon in the Dock.
In the Choose Library dialog, select the library you want to import photos into, then click Choose Library.
Choose File > Import, navigate to the location of the library you want to import from, select it, then click Review for Import.
Note: If you participate in an iCloud Shared Photo Library, click the Library pop-up menu in the toolbar and choose the library to import into.
Do one of the following:
Import the entire library: Click Import All New Items.
Import selected photos: Select the photos to import, then click Import Selected.
If the two libraries contain duplicate photos, the duplicates appear in the library you imported the photos into. Click Duplicates in the sidebar to view the duplicates (the Duplicates item appears only when the library contains duplicates).