Thumbnail size and sort order
Make the thumbnails in the grid larger or smaller with one slider, and list the newest or the oldest photos first.
The grid button in the top bar opens a small panel with these two settings. Its tooltip shows the current size, for example Tile size — 180px.
Tile size
Drag the Tile size slider to make the tiles larger or smaller. The grid behind the panel changes as you drag, so the grid is its own preview. The labelled marks on the track are landmarks only; any size between the smallest and the largest is allowed.
The size is the largest a tile may grow to: the grid fills each row exactly with tiles of that size or a little smaller, so a row never ends in a gap. The setting is remembered.
Order
Order by newest first lists every grid with the most recent photos at the top. Turn it off to see the oldest first.
The button is not shown in the Duplicates view, which lays out its own groups.