In a recent project, I wanted to create a diagram of a repository for the appendix of a paper, including comments to highlight key files and explain how the folders were organised. I found this answer on Stack Exchange by user Gonzalo Medina, which I tweaked to produce the diagram below.

The code is below:

% Adapted from https://tex.stackexchange.com/a/270761

\documentclass[tikz,border=5mm]{standalone}
\usepackage[edges]{forest}

\definecolor{foldercolor}{RGB}{124,166,198}
\newcommand{\size}[2]{{\fontsize{#1}{0}\selectfont#2}}
\definecolor{blue}{RGB}{0,50,200}
\newcommand{\comment}[0]{\color{blue} \rm}

\tikzset{pics/folder/.style={code={%
\node[inner sep=0pt, minimum size=#1](-foldericon){};
\node[folder style, inner sep=0pt, minimum width=0.3*#1, minimum height=0.6*#1, above right, xshift=0.05*#1] at (-foldericon.west){};
\node[folder style, inner sep=0pt, minimum size=#1] at (-foldericon.center){};}
},
pics/folder/.default={20pt},
folder style/.style={draw=foldercolor!80!black,top color=foldercolor!40,bottom color=foldercolor}
}

\forestset{is file/.style={edge path'/.expanded={%
([xshift=\forestregister{folder indent}]!u.parent anchor) |- (.child anchor)},
inner sep=1pt},
this folder size/.style={edge path'/.expanded={%
([xshift=\forestregister{folder indent}]!u.parent anchor) |- (.child anchor) pic[solid]{folder=#1}}, inner xsep=0.6*#1},
folder tree indent/.style={before computing xy={l=#1}},
folder icons/.style={folder, this folder size=#1, folder tree indent=3*#1},
folder icons/.default={12pt},
}

\begin{document}

\begin{forest}
for tree={font=\ttfamily, grow'=0, folder indent=.9em, folder icons}
[repository
[data
[cleaned\_plants\_database
[experts\_extant.csv {\comment (which species are common and extant according to experts)}, is file]
[merged.csv {\comment (the plants database merged from different herbaria and museums)}, is file]
]
[processed
[first\_last\_detns\_final.csv {\comment (input to SEUX model)}, is file]
]
]
[undetected\_extinctions {\comment (shared SEUX model functions)}
]
]
\end{forest}

\end{document}