<b>Rows, layout and drag &amp; drop</b>

The figure is a stack of rows, 1 to 8 of them, each holding up to 4 traces. Rows share one
time axis and one pair of side margins, so their y labels line up, their data areas start and
end on the same two columns, and their windows cannot drift apart. The left margin holds the y
labels; the right one is empty, and is there so the newest tick's label and the newest sample's
ink have somewhere to land instead of sitting on the frame.

<b>How to reach it</b>

Drag a signal's chip out of the side panel (<tt>s</tt>) and drop it on a row to add a trace.
Press <tt>l</tt>, or pick <b>Layout editor</b> from the overflow menu, to add and remove rows:
a <tt>×</tt> appears at the top left of each row and a <tt>+</tt> on each boundary between
rows, including above the first and below the last. The editor's own button in the top-right
corner leaves it.

<b>Worth knowing</b>

• A plot's own <b>right-click menu</b> (the same compact rows as the app's menu) holds the
  y-axis scale, the two fits, and <b>Remove signal</b>, which swaps the menu to that plot's traces
  plus <i>All traces on this plot</i> — with a <b>Back</b> row to return. That is how a trace comes
  off a row without going through the layout editor.
• A drop <i>adds</i> a trace to the row's next free slot; it does not replace one. With four
  traces already on a row the drop is refused.
• Inserting a row moves the rows below it <i>with their contents</i>. Inserting above row 1
  puts what row 1 plotted onto row 2 and leaves the new row empty — the rows are not
  renumbered under you.
• A trace is remembered by the signal's <i>name</i>, not by its channel number, because a new
  CONFIG or an enable renumbers the channels and an index would silently re-point the trace.
• Adding or removing a row rebuilds the figure, which is cheap, but it also re-deals every
  trace. A frozen trigger event survives the rebuild: the pinned window is restated rather
  than re-framed on the live edge.

<b>Example</b>

With three traces on row 1, pressing <tt>l</tt> shows 3 buttons (one <tt>×</tt>, two
<tt>+</tt>). Clicking the <tt>+</tt> above row 1 gives 2 rows and 5 buttons, with the three
traces now on row 2 — the layout probe reports exactly this as
<tt>rows=2 buttons=5 traces=[0:-|1:sine,ramp,noise]</tt>.
