- One-row toolbar: groups fold into dropdowns by priority so the row never
  overflows; on macOS and GNOME the row is the title bar. The search box folds
  to an icon and overflowing section tabs scroll with faded edges.
- Popups: every popup animates as one composited layer, clipped to its rounded
  outline, with rows fixed while it opens; dialogs and menus share one tilt.
- Page Color menu: colour swatches, background art and rule lines. Rule lines
  are read, drawn and written as OneNote stores them; colour and rule changes
  undo in one step without reloading the page.
- Insert Space, matching OneNote 2010, including splitting crossed outlines and
  moving ink by offset.
- Search results pane and Tags Summary (#28); command palette (#19) with pages
  from every section; tag artwork for all 29 default tags.
- macOS trackpad pinch, smart zoom and swipe navigation (#16); Show in Finder in
  the sync popup, including notebooks on mounted shares.
- GNOME: libadwaita window edge and rounded bottom corners (#45); GNOME and KDE
  styled menus.
- Mac OS X 10.6: Aqua scrollers painted by AppKit, the resize grip, date picker
  Return, and a crash fix for the missing move cursor.

Assisted-by: claude-opus-5.5