I am wondering if there is a way to automatically set a symbol (eg. ►) somewhere at the end of an odd page every time a section is being continued on the following even page?
Manually this could be done by putting eg. \vfill\hfill$\triangleright$ after the last line of the odd page. But that doesn't work when the bottom line is full. And it's still no solution for a long document. And no solution at all when page breaks might still move.
So I thought maybe of something like a mark that appears next to the page number, something like this red triangle here:

Any idea how to create this?
Here's an MWE in which I left all the packages I am using in my document, in order to early recognize any conflicts.
\documentclass[10pt,twoside,titlepage,headsepline,headings=small,BCOR=8mm]{scrbook}
\usepackage{scrlayer-scrpage}
\usepackage{cmap}
\usepackage{ulem}
\usepackage[utf8]{inputenc}
\usepackage[vietnamese=nohyphenation]{hyphsubst}
\usepackage[vietnamese,polish]{babel}
\usepackage[T5,T1]{fontenc}
\usepackage{longtable}
\usepackage{lmodern}
\usepackage{makeidx}
\usepackage[columns=2,itemlayout=abshang,initsep=1.8em plus 0.2em minus 0.2em]{idxlayout}
\usepackage{mathtools}
\usepackage{graphicx}
\usepackage{etoolbox}
\usepackage{multirow}
\usepackage[table]{xcolor}
\usepackage[defaultlines=2,all]{nowidow}
\usepackage{lipsum}
\KOMAoptions{paper=24cm:17cm,DIV=14}
\setlength{\parindent}{0pt}
\setlength{\parskip}{1.2ex plus 0.8ex minus 0.4ex}
\setlength{\marginparwidth}{0pt}
\setlength{\marginparsep}{0pt}
\addtolength{\textheight}{0.4cm}
\addtolength{\headsep}{-0.4cm}
\addtolength{\topmargin}{-0.2cm}
\renewcommand{\chapterheadstartvskip}{\vspace{-\topskip}}
\preto{\addsec}{\vspace{\baselineskip}}
\hfuzz=2pt
\flushbottom
\clearmainofpairofpagestyles
\ihead[]{}
\chead[]{}
\ohead[]{\sffamily\leftmark}
\ifoot[]{}
\cfoot[]{}
\ofoot[]{}
\pagestyle{scrheadings}
\begin{document}
\mainmatter
\ofoot[\pagemark]{\pagemark}
\raggedbottom
\chapter{Chapter}
\addsec{Section 1}
\lipsum[5]
\lipsum[4]
\addsec{Section 2}
\lipsum[4]
\addsec{Section 3}
\lipsum[8]
\lipsum[6]
\addsec{Section 4}
\lipsum[3]
\lipsum[8]
\lipsum[7]
\addsec{Section 5}
\lipsum[4]
\lipsum[3]
\lipsum[2]
\addsec{Section 6}
\lipsum[8]
\lipsum[8]
\lipsum[1]
\addsec{Section 7}
\lipsum[9]
\end{document}
