- addon.arrange.randomizeOpacity, type.orientation.vertical and .horizontal,
type.opticalMarginAlignment, type.systemLayout and type.fractionalWidths
run through edit_if_changed (the Edit Colors helper) and record an undo step
only when an opacity, a direction or a setting changes.
- A test for each command; the params text says so, and docs/mcp.md for the
commands it describes.