Here is an addmargin
implementation that you can nest and adjust margins with, and also add "titles" with:

\documentclass{article}
\usepackage[margin=1in,showframe]{geometry}% Just for this example
\usepackage{lipsum}
\usepackage{xgalley}
\ExplSyntaxOn
% http://river-valley.zeeba.tv/media/conferences/tug-2015/0302-Joseph-Wright/
\cs_new_eq:NN \SetAbsMargins \galley_margins_set_absolute:nn % {<left margin>}{<right margin>}
\cs_new_eq:NN \SetRelMargins \galley_margins_set_relative:nn % {<left margin>}{<right margin>}
\ExplSyntaxOff
\newcommand{\inserttitle}{}
\newenvironment{addmargin}[2][40pt]
{%
\renewcommand{\inserttitle}[1]{%
\noindent\makebox[0pt][r]{\makebox[#1][l]{\bfseries ##1}}%
\ignorespaces}%
\SetRelMargins{#1}{#2}\ignorespaces}
{\par}
\begin{document}
\sloppy% Just for this example
\begin{addmargin}{0pt}
\inserttitle{Text}
\lipsum[11]
\lipsum[12]
\begin{addmargin}[75pt]{20pt}
\inserttitle{More text}
\lipsum[11]
\end{addmargin}
\inserttitle{Text\ldots}
\lipsum[13]
\end{addmargin}
\end{document}
The default left-margin width is 40pt.
labeling
) list. Or of marginal notes. Can you explain in more detail, what you are trying to achieve instead of saying how you can improve what you currently have?\begin{description}\item[Text} Sed ......
?