Add a note about dependency declarations in layouts/modules

lib/doc/Development.lyx

@@ -1434,6 +1434,86 @@ Modules do not need a template, only an example, which is strongly encouraged
  but not necessarily required.
 \end_layout
 
+\begin_layout Subsection
+Dependencies
+\end_layout
+
+\begin_layout Standard
+The declaration lines of layouts and modules (
+\begin_inset Flex Code
+status collapsed
+
+\begin_layout Plain Layout
+
+\backslash
+DeclareLaTeXClass
+\end_layout
+
+\end_inset
+
+, 
+\begin_inset Flex Code
+status collapsed
+
+\begin_layout Plain Layout
+
+\backslash
+DeclareLyXModule
+\end_layout
+
+\end_inset
+
+) should list the packages and classes the layout (or some\SpecialChar breakableslash
+one of the layouts\SpecialChar breakableslash
+inse
+ts of the module) needs.
+ Please do not add dependencies beyond this 
+\begin_inset Quotes eld
+\end_inset
+
+top level
+\begin_inset Quotes erd
+\end_inset
+
+, i.
+\begin_inset space \thinspace{}
+\end_inset
+
+e., packages that are needed by a required class or package itself (e.
+\begin_inset space \thinspace{}
+\end_inset
+
+g., 
+\begin_inset Flex Code
+status collapsed
+
+\begin_layout Plain Layout
+xcolor
+\end_layout
+
+\end_inset
+
+ as required by the 
+\begin_inset Flex Code
+status collapsed
+
+\begin_layout Plain Layout
+beamer
+\end_layout
+
+\end_inset
+
+ class).
+ Such lower level dependencies constantly change, so they differ between
+ class and package versions.
+ Thus, resolving such lower-level dependencies is a task of the respective
+ package manager of the \SpecialChar LaTeX
+ distribution (or your operating system).
+ \SpecialChar LyX
+ cannot reliably predict on a general level what a class package needs
+ (or even what the packages a class need themselves need).
+\end_layout
+
 \begin_layout Subsection
 Layouts for document classes with incompatible versions
 \end_layout