diff --git a/autotests/export/docbook/Linguistics_forest.lyx b/autotests/export/docbook/Linguistics_forest.lyx
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+#LyX 2.4 created this file. For more info see https://www.lyx.org/
+\lyxformat 608
+\begin_document
+\begin_header
+\save_transient_properties true
+\origin unavailable
+\textclass article
+\begin_preamble
+%% Uncomment the following for Tableaux captions on top:
+%\floatstyle{plaintop}
+%\restylefloat{tableau}
+
+% Backwards compatibility for forest 1.x
+% If you use forest 2.0.1 or later, you can delete this
+\@ifpackageloaded{forest}{%
+  \@ifpackagelater{forest}{2016/02/20}{}{%
+    \forestset{
+      roof/.style={edge path={\noexpand\path[\forestoption{edge}]%
+          (.north west)--(!u.south)--(.north east)--cycle
+          \forestoption{edge label};
+        }
+      },
+      sn edges/.style={
+        for tree={parent anchor=south, child anchor=north},
+      },
+      linguistics preamble/.style={sn edges, baseline, for tree={align=center}}
+    }
+    \preto\forest@do{%
+      \forestOpreto{\forest@root}{given options}{linguistics preamble,}%
+    }
+  }
+}{}
+\end_preamble
+\use_default_options false
+\begin_modules
+linguistics
+\end_modules
+\maintain_unincluded_children no
+\language english
+\language_package default
+\inputencoding utf8
+\fontencoding auto
+\font_roman "lmodern" "FreeSerif"
+\font_sans "default" "FreeSans"
+\font_typewriter "default" "FreeMono"
+\font_math "auto" "auto"
+\font_default_family default
+\use_non_tex_fonts false
+\font_sc false
+\font_roman_osf false
+\font_sans_osf false
+\font_typewriter_osf false
+\font_sf_scale 100 100
+\font_tt_scale 100 100
+\use_microtype false
+\use_dash_ligatures false
+\graphics default
+\default_output_format default
+\output_sync 0
+\bibtex_command default
+\index_command default
+\float_placement class
+\float_alignment class
+\paperfontsize default
+\spacing single
+\use_hyperref true
+\pdf_bookmarks true
+\pdf_bookmarksnumbered false
+\pdf_bookmarksopen false
+\pdf_bookmarksopenlevel 1
+\pdf_breaklinks false
+\pdf_pdfborder true
+\pdf_colorlinks false
+\pdf_backref false
+\pdf_pdfusetitle true
+\papersize default
+\use_geometry false
+\use_package amsmath 1
+\use_package amssymb 1
+\use_package cancel 1
+\use_package esint 1
+\use_package mathdots 1
+\use_package mathtools 1
+\use_package mhchem 1
+\use_package stackrel 1
+\use_package stmaryrd 1
+\use_package undertilde 1
+\cite_engine basic
+\cite_engine_type default
+\biblio_style plain
+\use_bibtopic false
+\use_indices false
+\paperorientation portrait
+\suppress_date false
+\justification true
+\use_refstyle 0
+\use_minted 0
+\use_lineno 0
+\index Index
+\shortcut idx
+\color #008000
+\end_index
+\secnumdepth 3
+\tocdepth 3
+\paragraph_separation indent
+\paragraph_indentation default
+\is_math_indent 0
+\math_numbering_side default
+\quotes_style english
+\dynamic_quotes 0
+\papercolumns 1
+\papersides 1
+\paperpagestyle default
+\tablestyle default
+\tracking_changes false
+\output_changes false
+\change_bars false
+\postpone_fragile_content false
+\html_math_output 0
+\html_css_as_file 0
+\html_be_strict false
+\docbook_table_output 0
+\docbook_mathml_prefix 1
+\end_header
+
+\begin_body
+
+\begin_layout Title
+Writing linguistic papers
+\end_layout
+
+\begin_layout Author
+Jürgen Spitzmülle
+\end_layout
+
+\begin_layout Section
+Linguistic structure trees
+\end_layout
+
+\begin_layout Standard
+Here is a simple example:
+\end_layout
+
+\begin_layout Standard
+\begin_inset Flex Structure Tree
+status open
+
+\begin_layout Plain Layout
+[VP [DP[John]] [V' [V[sent]] [DP[Mary]] [DP[D[a]][NP[letter]]] ] ]
+\end_layout
+
+\end_inset
+
+
+\end_layout
+
+\begin_layout Standard
+\noindent
+If you view the PDF output, you will see that the input
+\end_layout
+
+\begin_layout Quote
+
+\family typewriter
+\size small
+[VP [DP[John]] [V' [V[sent]] [DP[Mary]] [DP[D[a]][NP[letter]]]]]
+\end_layout
+
+\begin_layout Standard
+expands to a real structure tree.
+ To view the result within the work area, you can simply embed the Structure
+ Tree inset into a Preview inset.
+ If instant preview is correctly installed and activated, you should see
+ the tree immediately (just click on the image in order to edit):
+\end_layout
+
+\begin_layout Standard
+\begin_inset Preview
+
+\begin_layout Standard
+\begin_inset Flex Structure Tree
+status open
+
+\begin_layout Plain Layout
+[VP [DP[Mary]] [V' [V[sent]] [DP[John]] [DP[D[a]][NP[response]]] ] ]
+\end_layout
+
+\end_inset
+
+
+\end_layout
+
+\end_inset
+
+
+\end_layout
+
+\begin_layout Standard
+\noindent
+Roofs can be easily generated by means of the 
+\family typewriter
+roof
+\family default
+ option (note that the comma has special meaning, as it marks options):
+\end_layout
+
+\begin_layout Standard
+\begin_inset Flex Structure Tree
+status open
+
+\begin_layout Plain Layout
+[VP [DP[John]] [V' [V[sent]] [DP[Mary]] [DP[another letter, roof]] ] ]
+\end_layout
+
+\end_inset
+
+
+\end_layout
+
+\begin_layout Standard
+\noindent
+In order to align nodes of the tree more elegantly, use the 
+\begin_inset Quotes eld
+\end_inset
+
+tier
+\begin_inset Quotes erd
+\end_inset
+
+ option.
+ All nodes which have the same 
+\family typewriter
+tier
+\family default
+ allocated get aligned.
+ Here is an example:
+\end_layout
+
+\begin_layout Standard
+\begin_inset Flex Structure Tree
+status open
+
+\begin_layout Plain Layout
+[VP [DP[John,tier=word]] [V' [V[sent,tier=word]] [DP[Mary,tier=word]] [DP[D[a,ti
+er=word]][NP[letter,tier=word]]] ] ]
+\end_layout
+
+\end_inset
+
+
+\end_layout
+
+\begin_layout Standard
+\noindent
+The package supports many additional features, such as movement arrows and
+ decorations, that cannot documented here.
+\end_layout
+
+\end_body
+\end_document