With the Selection tool, a click (no drag, no modifier) on one object of a
selection of several makes it the key object (select.key); a click on the
key again lets it go. The key object is drawn with a thicker outline,
Align aligns to it (the Align panel shows Align to Key Object while there
is a key, and choosing Selection or Artboard lets it go), and
object.align without `to` aligns to the key when there is one, so the
Control bar's and the Properties panel's Align buttons do too. With a
spacing, Distribute Spacing keeps the key object still and spaces the
others from it, and it reports too few objects instead of indexing an
empty list.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>