I am more or less copying this answer. In order to have box, you need to put \StartBox in the line the box starts, and \EndBox in the line it ends. It supports page breaks. You need to compile up to three times.
\documentclass{article}
\usepackage{tikz}
\usepackage{refcount}
\usetikzlibrary{backgrounds,calc}
\usepackage{tikzpagenodes}
\usepackage{lipsum}
\tikzset{SimpleBox/.style={fill=gray,fill opacity=0.3}}
\newcounter{tmp}
\newcommand{\StartBox}[1][]{%
\stepcounter{tmp}%from https://tex.stackexchange.com/a/52579/121799
\tikz[remember picture,overlay, baseline=(Begin.base)]{%
\node[anchor=base,inner sep=0pt,outer sep=0pt] (Begin) {\strut};}
\label{a\thetmp}%
\ifnum\getpagerefnumber{a\thetmp}=\getpagerefnumber{b\thetmp} \else
\begin{tikzpicture}[overlay, remember picture]
\path (current page text area.north west) -- (current page text area.south west)
node(WestLine)[left]{};
\path (current page text area.north east) -- (current page text area.south east)
node(EastLine)[right]{};
\begin{scope}[on background layer,blend mode=multiply]
\draw[SimpleBox,#1] ($(current page text area.south-|WestLine)-(0,2pt)$)
-- (Begin.north-|WestLine) -- (Begin.north-|EastLine)
-- ($(current page text area.south-|EastLine)-(0,2pt)$);
\end{scope}
\end{tikzpicture}%
\fi%
}
\newcommand{\EndBox}[1][]{%
\tikz[remember picture,overlay, baseline=(End.base)]{%
\node[anchor=base,inner sep=0pt,outer sep=0pt] (End) {\strut};}%
\label{b\thetmp}
\ifnum\getpagerefnumber{a\thetmp}=\getpagerefnumber{b\thetmp}
\begin{tikzpicture}[overlay,remember picture]
\path (current page text area.north west) -- (current page text area.south west)
node(WestLine)[left]{};
\path (current page text area.north east) -- (current page text area.south east)
node(EastLine)[right]{};
\begin{scope}[on background layer,blend mode=multiply]
\draw[SimpleBox,#1] (Begin.north-|WestLine) rectangle (End.south-|EastLine);
\end{scope}
\end{tikzpicture}
\else
\begin{tikzpicture}[overlay,remember picture]
\path (current page text area.north west) -- (current page text area.south west)
node(WestLine)[left]{};
\path (current page text area.north east) -- (current page text area.south east)
node(EastLine)[right]{};
\begin{scope}[on background layer,blend mode=multiply]
\draw[SimpleBox,#1] ($(current page text area.north-|WestLine)+(0,2pt)$)
-- (End.south-|WestLine) -- (End.south-|EastLine)
-- ($(current page text area.north-|EastLine)-(0,2pt)$);
\end{scope}
\end{tikzpicture}
\fi
}
\newcommand{\SimpleBox}[2][]{%
\StartBox[#1]%
#2\EndBox[#1]}
\begin{document}
\begin{enumerate}
\item[1.] Structural and drafting enhancements developed under the International Ethics Standards Board for Accountants (IESBA) Structure of the Code project;
\item[2.] \StartBox Revisions to the provisions pertaining to safeguards in the Code, developed under the IESBA Safeguards project;
\item[3.] Revisions to clarify the applicability of the provisions in Part C of the extant Code to members in public practice, developed under the IESBA Applicability project (paragraphs R120.4, R300.5 and 300.5 A1);
\EndBox
\item[4.] New application material relating to professional skepticism and professional judgment, developed under the IESBA Professional Skepticism (short-term) project (paragraphs 120.5 A1, 120.5 A2, 120.5 A3, 120.13 A1 and 120.13 A2)
\end{enumerate}
\begin{enumerate}
\item[\textbullet] Structural and drafting enhancements developed under the International Ethics Standards Board for Accountants (IESBA) Structure of the Code project;
\item[\textbullet] \StartBox Revisions to the provisions pertaining to safeguards in the Code, developed under the IESBA Safeguards project;
\item[\textbullet] Revisions to clarify the applicability of the provisions in Part C of the extant Code to members in public practice, developed under the IESBA Applicability project (paragraphs R120.4, R300.5 and 300.5 A1);
\EndBox
\item[\textbullet] New application material relating to professional skepticism and professional judgment, developed under the IESBA Professional Skepticism (short-term) project (paragraphs 120.5 A1, 120.5 A2, 120.5 A3, 120.13 A1 and 120.13 A2)
\item[\textbullet] Revisions to address preparation and presentation of information and pressure to breach the fundamental principles, developed under the IESBA Part C project - Phase 1 (sections 220 and 270); and
\item[\textbullet] \StartBox Revisions to the provisions pertaining to the offering and accepting of inducements, developed under the IESBA Part C project - Phase 2 (sections 250 and 340).
\item[\textbullet] Hibernation is very important.
\item[\textbullet] Honey liquor is also important.\EndBox
\end{enumerate}
\begin{enumerate}
\item[1.] Structural and drafting enhancements developed under the International Ethics Standards Board for Accountants (IESBA) Structure of the Code project;
\item[2.] \StartBox Revisions to the provisions pertaining to safeguards in the Code, developed under the IESBA Safeguards project;
\item[3.] Revisions to clarify the applicability of the provisions in Part C of the extant Code to members in public practice, developed under the IESBA Applicability project (paragraphs R120.4, R300.5 and 300.5 A1);
\EndBox
\item[4.] New application material relating to professional skepticism and professional judgment, developed under the IESBA Professional Skepticism (short-term) project (paragraphs 120.5 A1, 120.5 A2, 120.5 A3, 120.13 A1 and 120.13 A2)
\end{enumerate}
\begin{enumerate}
\item[\textbullet] Structural and drafting enhancements developed under the International Ethics Standards Board for Accountants (IESBA) Structure of the Code project;
\item[\textbullet] \StartBox Revisions to the provisions pertaining to safeguards in the Code, developed under the IESBA Safeguards project;
\item[\textbullet] Revisions to clarify the applicability of the provisions in Part C of the extant Code to members in public practice, developed under the IESBA Applicability project (paragraphs R120.4, R300.5 and 300.5 A1);
\EndBox
\item[\textbullet] New application material relating to professional skepticism and professional judgment, developed under the IESBA Professional Skepticism (short-term) project (paragraphs 120.5 A1, 120.5 A2, 120.5 A3, 120.13 A1 and 120.13 A2)
\item[\textbullet] Revisions to address preparation and presentation of information and pressure to breach the fundamental principles, developed under the IESBA Part C project - Phase 1 (sections 220 and 270); and
\item[\textbullet] \StartBox Revisions to the provisions pertaining to the offering and accepting of inducements, developed under the IESBA Part C project - Phase 2 (sections 250 and 340).
\item[\textbullet] Hibernation is very important.
\item[\textbullet] Honey liquor is also important.\EndBox
\end{enumerate}
\end{document}

tikzmark(may be a custom one) fromtikzpackage – koleygr Nov 21 '19 at 11:30