An alternative would be hiding the photos from the library.
This used to work well in the early system versions. Hiding made the photos visible in the library, but kept them visible in the albums, just what you want to do.
Only, apple has changed the "Hide" tool to a toll to keep confidential photos secret, so we can no longer see in the albums.
On your Mac you can make the hidden photos in an album visible with a smart album. Any smart album with a rule "Photo is Hidden" will show you the hidden photos that are matching the rules for the smart album.
For example, if you have an album named "My Great Album" and you have hidden the photos inside this album from the library, create a smart album with the following rules:
- File > New Smart album:
- Match all:
- Album > Is > My Great Album
- Photo> is > Hidden
This companion will be showing you the hidden photos from "My Great Album".