I've looked in Chapter 5 of the Users Guide and the latest edition of Herbert's Math-mode book, as well as on the math panel and Edit->Math menu without seeing how to enter a vertical vector with brackets on either side.
I've tried using the matrix mode from the math panel, with 2 columns and 3 rows and I can get:
W_1 W = W_2 W_3
but I cannot get square brackets on either side of the vector. I can do this for a single cell, but not all three. It must be something simple I've missed.
insert \[W = \begin{bmatrix}W_1\\W_2\\W_3\end{bmatrix}\]
mark it with the cursor/mouse and hit ctrl-m andbe sure, that use amsmath is enabled. Do _not_ use brackets and an array. p. 57 in my math doc
Herbert
