Adding "Cited as" next to each bibliography item in the bibliography of a thesis

Question

I am working on a thesis (in french), and using biblatex to manage my citations with geschichtsfrkl as the style for defining citations. In my thesis, I am using \printbibliography to display all my citations in the Bibliography chapter.

My university asks specifically about adding "cited as (cité in french)" next to each item in the bibliography (refer to the following examples):

Asimov Issac, The naked Sun, London 2018. (cité : Asimov.)

Algan Yann / Cazenave Thomas, L'État en mode start-up, 1e éd., Paris 2016. (cité : Algann / Cazenave.)

I searched a lot and understood that this is some sort of back referencing, and the "cited as" that I want is the short citation format that uses the last names (in Small Capitals) separated by a slash (/).

But, I don't know how to achieve it. Any help would be greatly appreciated. Many thanks in advance.

Following is a MWE:

\documentclass[
    french,
    10 pt,              
    openright
]{article}              
\usepackage[utf8]{inputenc}
\usepackage[style=geschichtsfrkl,
backend=biber,
sorting=nyt]{biblatex}
\addbibresource{\thesis.bib}
\usepackage{filecontents}
\begin{filecontents}{\thesis.bib}
@article{deroudille2019extraterritorialite,
  title={L’extraterritorialit{'e} du RGPD dans le contexte du “Cloud Act”},
  author={Deroudille, Alexis and Fatah, Farid},
  journal={Revue du marche commun et de l'Union Europ{'e}enne},
  number={630},
  pages={442--452},
  year={2019},
  publisher={{'E}ditions Techniques et Economiques}
}
@article{decaux1987application,
  title={L'application extraterritoriale du droit {'e}conomique},
  journal = {Cahiers du Centre de Droit International de Nanterre},
  number = {3},
  author={Decaux, Emmanuel},
  year={1987},
  publisher={JSTOR}
}
@article{lehmann_m_legal_2017,
    title = {Legal fragmentation, extraterritoriality and uncertainty in global financial regulation},
    volume = {37},
    issn = {0143-6503},
    %language = {English},
    number = {2},
    journal = {Oxford Journal of Legal Studies},
    author = {{Lehmann}, Matthias},
    pages = {406-434},
    year = {2017},
    note = {OCLC: 7086651768},
    pages = {406--434}
}
\end{filecontents}
\begin{document}
\chapter{Bibliographie}
\nocite{*}
\printbibliography
\end{document}

Answer 1

The following adds a "cited as"/"cité" info to the bibliography that relies on cite:short. So the output there should be the same output you get in the citations if you cite the entry multiple times.

I took the code for the citedas macro from my answer to Formatting issue with DeclareBibliographyDriver in my Custom Biblatex Style based.

\documentclass[french]{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{babel}
\usepackage{csquotes}

\usepackage[backend=biber,
  style=geschichtsfrkl,
  sorting=nyt,
  citecounter,
]{biblatex}

\DefineBibliographyStrings{french}{
  citedas = {cit\'e},
}

\renewbibmacro*{finentry}{%
  \ifbibliography
    {\setunit{\finentrypunct\space}%
     \ifnumgreater{\value{citecounter}}{0}
       {\usebibmacro{citedas}%
        \renewcommand*{\finentrypunct}{}}
       {}}
    {}%
  \finentry}

\newbibmacro{citedas}{%
  \printtext[parens]{%
    \bibstring{citedas}%
    \addcolon\space
    \usebibmacro{citedas:cite}}}

\makeatletter
\newbibmacro{citedas:cite}{%
  \begingroup
    \delimcontext{cite}%
    \DeclareFieldFormat{bibhyperref}{##1}%
    \csuse{blx@hook@cite}%
    \csuse{blx@hook@citekey}%
    \undef\cbx@lasthash
    \undef\cbx@lastyear
    \citetrackerfalse\pagetrackerfalse\backtrackerfalse
    \defcounter{maxnames}{\blx@maxcitenames}%
    \usebibmacro{cite:short}%
  \endgroup
}
\makeatother



\begin{filecontents}{\jobname.bib}
@article{deroudille,
  title   = {L'extraterritorialité du RGPD dans le contexte du “Cloud Act”},
  author  = {Deroudille, Alexis and Fatah, Farid},
  journal = {Revue du marche commun et de l'Union Européenne},
  number  = {630},
  pages   = {442--452},
  year    = {2019},
}
@article{decaux,
  title   = {L'application extraterritoriale du droit économique},
  journal = {Cahiers du Centre de Droit International de Nanterre},
  number  = {3},
  author  = {Decaux, Emmanuel},
  year    = {1987},
}
@article{lehmann,
  title   = {Legal fragmentation, extraterritoriality and uncertainty
             in global financial regulation},
  volume  = {37},
  issn    = {0143-6503},
  number  = {2},
  journal = {Oxford Journal of Legal Studies},
  author  = {Lehmann, Matthias},
  pages   = {406-434},
  year    = {2017},
  note    = {OCLC: 7086651768},
  pages   = {406--434},
}
\end{filecontents}
\addbibresource{\jobname.bib}

\nocite{*}

\begin{document}
Lorem\footcite{lehmann} ipsum\footcite{decaux}
Lorem\footcite{lehmann} ipsum

\printbibliography
\end{document}