Accessing and changing biblatex.cfg in Overleaf

Question

I use Overleaf to write LaTeX-documents, but my department requires a very specific bibliography style. According to this guide I need to temper with biblatex.cfg and bibltex.def. Where can I find and change them in Overleaf, if at all? And what would be a good alternative? (Learning to use LaTeX on my computer isn't really an option due to due dates).

For reference: the guidelines pp.31-43 (in german)

Example:

Name, First name / Name, First name: „Article title. Subtitle“, in: Name, First name / Name, First name (Hrsg.), Book title. Subtitle, Publishing place(s): Publisher year, S. x-y.

Answer 1

You don't have direct access to the TeX system used by Overleaf, so accessing system files is not easy. But it should not be necessary in your case anyway.

The default biblatex.cfg is functionally empty. So you could just create a new empty file on Overleaf and use that.

But I wouldn't even do that. I disagree about biblatex.cfg with https://tex.stackexchange.com/a/13076/35864 (and answer that I hold in very high regards). biblatex.cfg is supposed to be a global configuration file that is loaded by all documents loading biblatex. That means that it can be sort of "invisible" to you that the file is used and loaded until you check the .log file. This can lead to confusion and unexpected output.

There are many places where you can put your biblatex modifications (Biblatex.cfg vs .cls vs .sty), but unless they are really long I think the preamble is the best place: That way you always see your modifications right away so you can never be surprised by them.

Just from the example you gave in your question you might want to try something like

\documentclass[ngerman]{article}
\usepackage[T1]{fontenc}
\usepackage{babel}
\usepackage{csquotes}
\usepackage[backend=biber, style=ext-verbose-ibid, innamebeforetitle]{biblatex}
\renewcommand*{\newunitpunct}{\addcomma\space}
\DeclareNameAlias{sortname}{family-given}
\DeclareNameAlias{ineditor}{sortname}
\DeclareDelimFormat{multinamedelim}{\addspace\slash\space}
\DeclareDelimAlias{finalnamedelim}{multinamedelim}
\DeclareDelimFormat{editortypedelim}{\addspace}
\DeclareFieldFormat{editortype}{\mkbibparens{#1}}
\DeclareDelimAlias{translatortypedelim}{editortypedelim}
\DeclareFieldAlias{translatortype}{editortype}
\DeclareDelimFormat[bib]{nametitledelim}{\addcolon\space}
\renewcommand*{\subtitlepunct}{\addperiod\space}
\addbibresource{biblatex-examples.bib}
\begin{document}
Lorem \autocite{sigfridsson}
ipsum \autocite{sigfridsson}
dolor \autocite{pines}
sit \autocite{worman}
amet \autocite{pines}
consectur \autocite{nussbaum}
\printbibliography
\end{document}

Just for fun, here is a little trick to access system files on Overleaf. You use cp in a shell escape, to copy the file into the working directory so that it can be accessed via "Other logs and files" (cf. Overleaf V2 - How to get BBL File?).

\documentclass[british]{article}
\usepackage[T1]{fontenc}
\usepackage{babel}
\usepackage{csquotes}
\usepackage[backend=biber, style=authoryear]{biblatex}
\usepackage{shellesc}
\ShellEscape{%
  cp $(kpsewhich biblatex.def) .
}
\addbibresource{biblatex-examples.bib}
\begin{document}
Lorem \autocite{sigfridsson}
\printbibliography
\end{document}