What variables live in what include file?

cpanel.h  : ui variables that live in the control panel; they
            could also be in ggobi.h, in a way, because there's
            one of them per ggobi instance.
datad.h   : in the case that we might have multiple data arrays --
            node variables and edge variables in the graph case,
            or just two different data arrays, for some reason we
            haven't thought of yet
display.h : variables that are per-display -- ie, per window
ggobi.h   : variables that are per-ggobi (I can't imagine dealing
            with multiple ggobi's but Duncan allowed for that in
            the R interface)
splot.h   : variables that are per-plot (do we ever want
            to support multiple tours in the same window?)

vartable.h : the data for each variable is described here.

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How does one keep the console panels in sync when switching between
  displays in the same view mode?

Use the routines with names like cpanel_brush_set.

get a pointer to the widget using widget_find_by_name
    (having named the widget when it was created)
set the appearance of the widget to match the corresponding variable
     
To set the name:
  gtk_widget_set_name (option_menu, "BRUSH:linkby_option_menu"); 
To get the widget by name:
  w = widget_find_by_name (pnl, "BRUSH:linkby_option_menu");
  
The name can be any string, of course; I adopted a pretty
verbose naming convention to make sure I could find the names
easily when editing or grepping the code.
    
To set the widget's appearance:

For a toggle button:
  GTK_TOGGLE_BUTTON (btn)->active = cpanel->brush_on_p;
  
For an option menu:
  gtk_option_menu_set_history (GTK_OPTION_MENU (w), cpanel->br_linkby);
  

