I am using LyX and would like to create a document with 3 vertical columns. I noticed there was a built-in option for 2 columns, i.e. Document->Settings->Text Layout->Two-column document. Is there an option for 3 columns? If not, is it possible to create it with a LaTeX preamble? (at the beginning of the LyX document)
You can use the
to the LaTeX preamble (Document -> Settings -> LaTeX preamble).
You also need to insert two lines of ERT
Everything between these two is now in a three-column layout.