The solution is to simply add \justify
or \wordwrap
to the \markup
command, as:
\version "2.17.25"
{
\footnote #'(-1 . 1)
\markup\justify{Lorem ipsum dolor sit amet, consectetur adipiscing elit. Ut eget ante venenatis mi consectetur ornare. Cras facilisis dictum venenatis. Donec.}
a'4 b' c'' d''
}