I have migrated my 200 gigabyte Photos library to iCloud on my Mac. Works very well.
I then created a new, empty library on the Mac and let Photos copy the whole iCloud contents locally on the Mac. Now I need the space locally, so I would like Photos to undo the local copying only leaving the preview image locally and release say 150 Gb of the 200. Clicking the “Optimize Mac-storage” radio button in preferences (and waiting days while having About this Mac -> System report -> Storage administration open) does not do this.
Is there a way to trigger this process? Is the only way to delete my current library, create a new empty library on the Mac, and let it populate?