I just downloaded the package
stmaryrd and have a LyX LaTeX Beamer document in which I want to insert some symbols with this package (
\llbracket). Is there a way to make LyX include the package in the file, without having to edit the underlying document outside of LyX? Thanks!
LyX has an option to edit the LaTeX preamble (under Document > Settings > LaTeX Preamble), and in there you can insert:
And then you can insert the symbols you need using its feature for inserting LaTeX codes directly.
Getting the symbols to appear correctly in the LyX preview screen is another matter, and probably very difficult if not impossible, however.