title: LaTeX: Indent subcaption in figure environment
body: <p>See this MWE:</p>
  
  <pre><code>% !TeX spellcheck = en_US
  \documentclass[12pt]{article}
  \usepackage[onehalfspacing]{setspace}
  \usepackage[a4paper, margin=2.5cm]{geometry}
  \usepackage{mathptmx}
  \usepackage{amsmath}
  \usepackage{graphicx}
  \usepackage[hang]{caption}
  \usepackage{subcaption} 
  \usepackage[bottom]{footmisc}
  \usepackage{dcolumn} %makes r output work
  \usepackage{tabularx}
  \newcolumntype{L}[1]{&gt;{\raggedright\arraybackslash}p{#1}}
  \newcolumntype{C}[1]{&gt;{\centering\arraybackslash}p{#1}} 
  \newcolumntype{R}[1]{&gt;{\raggedleft\arraybackslash}p{#1}} 
  \newcommand{\possessivecite}[1]{\citeauthor{#1}'s (\citeyear{#1})}
  \usepackage{pdfpages}
  \usepackage{hyperref}
  \usepackage{pdflscape}
  \usepackage{xcolor}
  \usepackage{tikz}
  \usetikzlibrary{calc}
  
  \begin{document}
  
  \begin{landscape}
      \setcapmargin[2cm]
  
  \begin{figure}[]
      \captionsetup{justification=centering}
      \caption{Main Caption. } 
      \label{fig:val_efcts}
      \begin{subfigure}{0.55\textwidth}
          \caption{X}
          \includegraphics[width=\textwidth] {example-image-a}
      \end{subfigure}
      \begin{subfigure}{0.55\textwidth}
          \caption{Y}
          \includegraphics[width=\textwidth] {example-image-b}
      \end{subfigure}
      \begin{subfigure}{0.55\textwidth}
          \caption{Z}
          \includegraphics[width=\textwidth] {example-image-c}
      \end{subfigure}
      \captionsetup{justification=raggedright}    \subcaption*{This subcaption is supposed to be ragged right and intented by 4 cm. \\ This is in a new line.}
  \end{figure}
  
  \end{landscape}
  
  \end{document}
  </code></pre>
  
  <p>It should be self-explanatory, mostly. I'd like the last subcaption below the picture to be ragged right, but indented 2 cm. I tried to use \setcapmargin, but that does not work, creating the "undefined control sequence" error (so it's an unknown command). </p>