Changing a Math-mode matrix. How?

[R. Lahaye]

Hi,

I have in Display mode a Math-matrix with certain dimensions
all set up with beautiful formulas already.

However, I need to add another row to this matrix.
Is there a LyX tool to do that (similar to add/change
the dimensions of a table) ?

The Matrix in the Math-panel seems always to add a new matrix
from scratch......

Thanks,

Rob.

PS: if there's no tool for this, then
   would I lose information when I save the file as TeX, edit the TeX
   file (add row to matrix) and then load it again in LyX ?