Slots: a frame of a main component becomes a slot property
(component.makeSlot / removeSlot, preferred components, type "slot" in
component.properties). Instances show the main's default content until
the slot is edited; from then on its layers are the instance's own
(override group "slot"): free to add, remove and reorder, kept across
main updates, variant switches, copy/paste and detach, and instances
placed there stand alone. instance.slotInsert fills a slot,
instance.resetSlot brings the default content back. Structure
protection allows edits inside slots only; drops from the Assets panel,
canvas drags, drawing and paste land in slots. UI: slot icon in the
layers panel, dashed outlines and labels on the canvas, slot property
rows with a fill menu in the properties panel, Make/Remove slot on
frames inside a main.
Nested overrides: overrides inside a nested instance survive the main
moving it into another frame (layers matched by source alone when
unique); a nested instance copied out of an instance is re-linked to
its own main with its look kept (values set by component properties
aren't overrides); plain layers copied out of instances stop mirroring
them; canvas drags can no longer pull layers out of an instance or
reorder its auto layout children. Tests for swaps, variant switches,
main restructuring, detach and copy/paste.
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>