Nice boxes listed

\documentclass[11pt,parskip=half,numbers=noenddot,bibliography=totoc,index=totoc,
  listof=leveldown
]{scrbook}

\addtotoclist{loe}
\newcounter{example}[chapter]
\renewcommand{\theexample}{\thechapter.\arabic{example}}
\newcommand{\listofloename}{List of Examples}
\newcommand\listofexamples{\listoftoc{loe}}
\setuptoc{loe}{chapteratlist,leveldown}
\makeatletter
\newcommand\l@example{\l@figure}
\makeatother

\usepackage{tcolorbox}
\newenvironment{example}[1]{%
  \setlength\parfillskip{0pt plus 1fil}%
  \begin{tcolorbox}[
    before title={%
      \refstepcounter{example}%
      \addxcontentsline{loe}{section}[\theexample]{\ignorespaces #1}},
    title=Example\ \theexample:\ \ignorespaces #1]%
}{\end{tcolorbox}}

\begin{document}
\chapter{First}

\begin{example}{First example.}
\end{example}
\begin{table}
\caption{First graph.}
\end{table}

\chapter{Second}
\begin{example}{Second example.}
    Very nice!
\end{example}
\begin{table}
\caption{Second graph.}
\end{table}
\begin{example}{Third example.}
\end{example}
\begin{table}
\caption{Third graph.}
\end{table}

\chapter{Lists}
\listoftables
\listofexamples
\end{document}