please see if this suits your requirement -- code edited from -- short vertical line in footer fancyhdr
You can experiment with \hspace{-4cm} for moving the entire line left or right toward the page margins
You can experiment with \rule[10pt]{7cm}{6pt} to change the length height and thickness of the line alone
Disadvantages of using fancyhdr with KOMA are given at the website shortcut provided at top


\documentclass[12pt, a4paper,twoside,footheight=23pt]{scrreprt}
\usepackage{blindtext}% only for dummy text
\usepackage{xcolor}
\usepackage{scrlayer-scrpage}% sets pagestyle scrheadings automatically
\clearpairofpagestyles
\rofoot*{\vfootline\hspace{-4cm}\pagemark}
\lefoot*{\pagemark\hspace{-4cm}\vfootline}% for twosided document
\newlength\linepagesep
\setlength{\linepagesep}{5pt}
\newcommand*\vfootline{\textcolor{blue}{\rule[10pt]{7cm}{6pt}}}
\begin{document}
\blinddocument
\end{document}
Other example