doc revision

[Werner]

I could imagine something like that:

NR

1.1.4 
Note heads

add:
See also:
formatting cue notes

1.6.3
formatting cue notes

add:
One can obtain cue notes starting a cue voice:

{ \times 2/3 {g4 g g } \times 2/3 {a4 a a} | 
\times 2/3 {b4 b b} \times 2/3 {cis4 d e} | 
a,1 | \new CueVoice { r8 a \noBeam h-^ a c-^ a \noBeam cis-^ a | 
d2 c~ | c2 es4 d | } d1~ | d2 c4 b | a2 g2~ | g2. r4 | }

Often cue-notes are given as alternative to other notes or to rests. 
(Cuenotes often are added to rests in one voice quoting other voices, 
to find the start after the rests, see examples below, about quoting 
see section above). (Alternatives can also be given as ossia, see ossia.)

Examples for alternative lower notes (using polyphony with << {} \\ {} >> 
see 1.5.2 The double backslash construct):

\clef G
\relative c''
{ h'2 a4 g | c2 d4 e | << { f2 g4 f } \\ \new CueVoice { e4 d e f } >> |  
e2 r | }

\clef "F"
\relative c, 
{ es4 es' << {es'4 d8 d~ | d4 f cis8 a f es | d4 c' c h8 b~ | b1 | } \\ 
\new CueVoice { \stemDown es,4 d8 d~ | d4 f cis8 a f es | d4 c' c h8 b~ | 
b1 | \stemNeutral } >> r4 r8 b' a4. g8 | f4 es8 d~ d2 | }

(Warning: the CueVoice behaves like OneVoice also in the \\ polyphony 
context. Therefore add stemDirection.)

Example for alternative higher notes:

{
\clef F
\relative c 
{ es4 es <<\new CueVoice { \stemUp es } \\ es, >> es' | c g' c,2 }
% or
% { <<\new CueVoice { s4 s \stemUp es s} \\ { es es es, es' } >> | 
c g' c,2 } 
}
% % strange accidentals

BTW:
For better searching-results, sometimes add different words, e.g. 
cuenotes beside cue notes beside cue-notes, invisible beside hidden, ....

Werner