\documentclass{article}
\usepackage[ngerman]{babel}
\usepackage[
style=ext-authortitle-ibid,
backend=biber,
ibidtracker=constrict,
idemtracker=constrict,
loccittracker=constrict,
]{biblatex}
\usepackage{filecontents}
\begin{filecontents*}{\jobname.bib}
@book{test2019,
Author = {Max Mustermann and Maria Musterfrau and Peter Pan},
title = {Test},
pages ={123-234},
series = {Eine Reihe von Buechern}
}
@book{test2018,
title = {Test},
pages ={123-234},
series = {Eine Reihe von Buechern}
}
\end{filecontents*}
\addbibresource{\jobname.bib}
\makeatletter
\def\blx@loccit@stricttracker#1{%
\global\csundef{blx@lastnote@#1@\abx@field@entrykey}%
\blx@ifcitesingle
{\blx@imc@iffieldundef{postnote}
{\@firstoftwo}
{\expandafter\blx@imc@ifpages
\expandafter{\abx@field@postnote}}
{\global\cslet{blx@lastnote@#1@\abx@field@entrykey}\abx@field@postnote
\xifinlistcs\abx@field@entrykey{blx@trackkeys@#1}
{}
{\listcsxadd{blx@trackkeys@#1}\abx@field@entrykey}}
{}}
{}}
\def\blx@loccit@numcheck#1{%
\blx@imc@iffieldundef{postnote}
{\ifcsundef{blx@lastnote@#1@\abx@field@entrykey}}
{\expandafter\blx@imc@ifpages
\expandafter{\abx@field@postnote}
{\blx@imc@iffieldequalcs{postnote}{blx@lastnote@#1@\abx@field@entrykey}}
{\@secondoftwo}}}
\makeatother
\newtoggle{cbx:droppageprefix}
\renewbibmacro*{cite:ibid}{%
\ifloccit
{\printtext[bibhyperref]{\bibstring[\mkibid]{ibidem}}%
\global\booltrue{cbx:loccit}}
{\printtext[bibhyperref]{\bibstring[\mkibid]{loccit}}%
\global\toggletrue{cbx:droppageprefix}}}
\renewbibmacro*{cite}{%
\global\boolfalse{cbx:loccit}%
\global\togglefalse{cbx:droppageprefix}%
\iffieldundef{shorthand} {\ifthenelse{
\ifciteibid\AND\NOT\iffirstonpage}
{\usebibmacro{cite:ibid}}
{\ifthenelse{\ifciteidem\AND\NOT\iffirstonpage}
{\bibstring[\mkibid]{idem\thefield{gender}}}
{\printnames{labelname}}
\setunit*{\printdelim{nametitledelim}}%
\usebibmacro{cite:title}}}%
{\ifthenelse{
\ifciteibid\AND\NOT\iffirstonpage}
{\usebibmacro{cite:ibid}}
{\ifthenelse{\ifciteidem\AND\NOT\iffirstonpage}
{\bibstring[\mkibid]{idem\thefield{gender}}}
{\printnames{labelname}}
\setunit*{\printdelim{nametitledelim}}%
\usebibmacro{cite:shorthand}}}
}%
\begin{document}
Test.\footcite[123]{test2019}
Test.\footcite[123]{test2019}\footcite[125]{test2019}\footcite[123]{test2018}
Test.\footcite[123]{test2018}
\printbibliography
\end{document}
Danke schon mal im Voraus.
