This is a MWE.
\documentclass{book}
\usepackage{lipsum}
% -------------------------------
% Counter
\newcounter{exercise}[chapter]
\renewcommand{\theexercise}{\thechapter.\arabic{exercise}}
% -------------------------------
% Exercises environment (list-based)
\newenvironment{exercises}
{%
\par\vspace{\baselineskip}%
\noindent\rule{\textwidth}{0.8pt}\par%
\vspace{0.5\baselineskip}%
\begin{list}{}{%
\setlength{\leftmargin}{0pt}%
\setlength{\itemindent}{0pt}%
\setlength{\listparindent}{0pt}%
\setlength{\labelwidth}{0pt}%
\setlength{\labelsep}{0pt}%
\setlength{\itemsep}{1.5\baselineskip}%
\setlength{\parsep}{0pt}%
\setlength{\topsep}{0pt}%
}%
}
{%
\end{list}%
\vspace{0.5\baselineskip}%
\noindent\rule{\textwidth}{0.8pt}\par%
\vspace{\baselineskip}%
}
% -------------------------------
% List of Exercises machinery
\newcommand{\listexercisename}{List of Exercises}
\makeatletter
\newcommand{\listofexercises}{%
\chapter*{\listexercisename}%
\@starttoc{loe}%
}
\newcommand\l@exercise[2]{%
\@dottedtocline{1}{1.5em}{2.3em}{#1}{#2}}
\makeatother
% -------------------------------
% Patch \item to also add to .loe
\let\olditem\item
\renewcommand{\item}[1][]{%
\refstepcounter{exercise}%
\addcontentsline{loe}{exercise}{Exercise~\theexercise\ifx\relax#1\relax\else: #1\fi}%
\olditem[\textbf{Exercise \theexercise}\quad]%
}
\begin{document}
\tableofcontents
\listoftables
\listofexercises
\chapter{Some basic mathematics}
\begin{table}
\centering
\begin{tabular}{c|c}
\hline\hline
(1,1) & (1,2) \\
\hline
(2,1) & (2,2) \\
\hline\hline
\end{tabular}
\caption{This is a table.}\label{tbl:1}
\end{table}
\chapter{Differentiable manifolds and tensors}
\section{Definition of a manifold}
\begin{exercises}
\item \lipsum[2][1-3] $a^{2}+b^{2}=c^{2}$
\begin{equation}
a^{2}+b^{2}=c^{2}
\end{equation}
\item \lipsum[2][1-3] $\exp(\mathrm{i}\pi)=-1$
\begin{equation}
\exp(\mathrm{i}\pi)=-1
\end{equation}
\item \lipsum[2][1-3] $\cos^{2}\theta + \sin^{2}\theta = 1$
\begin{equation}
\cos^{2}\theta + \sin^{2}\theta = 1
\end{equation}
\end{exercises}
\section{The sphere as a manifold}
\begin{exercises}
\item \lipsum[2][1-3] $E=\hbar \omega$
\begin{equation}
E=\hbar \omega
\end{equation}
\end{exercises}
\end{document}
问 How to define a custom counter for Exercises?