Of course you can
also do so in the whole score by specifying
\layout {
\context {
\Staff
\omit StringNumber
}
}
Or, even shorter:
\layout {
\omit Staff.StringNumber
}
I do not know if this is completely equivalent, but lately I find myself
writing \layout { \context { ... } } only for \consist'ing and
\remove'ing engravers.
Lukas
