Choosing keepers manually
While duplicate rules provide a very flexible way to decide which duplicate photos to keep and get rid of, sometimes you may still want to make some decisions yourself, rather than leaving everything up to the automated rules.
You can do this by selecting one or more photos, then clicking either the “Keeper” or “Trash” button at the bottom of the window to mark your selection to either be kept or trashed. Alternately, you can also control-click a photo and use the contextual menu, or press the return key to toggle a photo between keeper and trash.
Note that while duplicate rules will always leave at least one keeper in each duplicate group, if you’re changing actions manually, it is possible to mark all photos from a group to be trashed. Be careful when doing this, since you want to be sure you’re not deleting all copies of a photo unless you really want to get rid of them all.