How can I use menukeys inside a {forest} environment?
This is most likely caused by nesting tikzpicture
environments. The simplest way to get around it would be to save your keys in \sbox
es.
% !TEX TS-program = pdfLaTeX
\documentclass[12pt, a4paper]{article}
\usepackage[textwidth=16cm]{geometry}
\usepackage[utf8]{inputenc}
\usepackage{forest}
\usepackage{menukeys}
\newsavebox{\keyA}
\sbox{\keyA}{\keys{A}}
\newsavebox{\keyB}
\sbox{\keyB}{\keys{B}}
\begin{document}
\section{Menu structure}
The menu can be navigated with the keyboard, from the main menu you can press \keys{A} to go the menu 2 or \keys{B} to go to menu 3.
\begin{forest}
for tree={
font=\ttfamily,
grow'=0,
child anchor=west,
parent anchor=south,
anchor=west,
calign=first,
edge path={
\noexpand\path [draw, \forestoption{edge}]
(!u.south west) +(7.5pt,0) |- node[fill,inner sep=1.25pt] {} (.child anchor)\forestoption{edge label};
},
before typesetting nodes={
if n=1
{insert before={[,phantom]}}
{}
},
fit=band,
before computing xy={l=15pt},
}
[Main menu
[ \usebox{\keyA} $\rightarrow$ Menu 2
[Foo]
[Bar]
[Baz]
]
[\usebox{\keyB} $\rightarrow$ Menu 3
[Quux]
]
]
\end{forest}
\end{document}