Thank you for your suggestions!
> Without
> knowing wxmaxima, I would speculate that if you precede a newline with a
> backslash \, then this problem will disappear.
It seems that wxMaxima does not accept this form of masking
the newline, the any cr (with or without backslash) is ignored
while constructing the string.
(%i10) foo_str: " -- foo()\
\
see bar";
(%o10) -- foo()\see bar
> A guaranteed workaround is to define the doc string and pass it as
> the second argument to user_doc (see below). If wxmaxima continues to
> cause problems, you can concatenate lines and newlines with 'concat'.
Just I'm not aware of a way to produce the newline. Anyway,
using the documentation from a .mac file (providing a package
with the functions to be documented), it works with newlines,
which is enough for me. Only issue is then that with every
load("the_package.mac"), the maxima-userinfo.lisp is enlarged.
Thank you again,
Martin