"Duplicate originals" appears under the trash in the collections
sidebar while the catalog holds any, and Settings says how many there
are beside the other whole-library passes. Both open one page: every
group with its picture and paths, the copy that stays (tap another path
to change it), a per-group Include box, what the survivor will gain and
any flag, label or face conflict, and why a group was skipped.
The summary is the dry run -- "N groups, M files to trash, K skipped" --
and nothing moves until "Check" has read the copies and "Move M copies
to trash" is pressed. Both run on workers with progress on the page, in
the activity register and, for the move, on the library status line;
Stop ends a job between groups. When it ends the grid, the sidebar and
the trash are refreshed and the survivors' judgements are written to
their sidecars and XMP the way a rating keystroke writes them.
The page is paginated at 30 groups, so a redraw decodes 30 thumbnails
and previews 30 merges whatever the size of the library. Back and
Escape leave it like its own Back button.