const LAYOUT_STEP: &str = "\u{0}layout";Expand description
Marker in the undo stack for “a pane was dragged somewhere else”. The arrangement itself lives in
Layout’s own (much shorter) history — this only keeps Ctrl+Z stepping back in the right order.
ponytail: once the layout history has scrolled past its 20 entries the marker undoes nothing; deepen
the layout stack if that ever bites.