Excel's Next Corner of Selection (Ctrl+., Control+. on a Mac) moves the
active cell clockwise to the next corner of the selected area (top-left,
top-right, bottom-right, bottom-left) and keeps the area selected; the
new active cell is also the anchor, so Shift+arrows then move the
opposite corner. GridCraft had no such command.
New command selection.nextCorner (Selection::next_corner) bound to
Ctrl+. on every platform. A one-row or one-column area goes end to end;
a single cell stays where it is.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>