One the beauties of LibreOffice is indeed it's use of LaTex math allowing for rapid and easy work with math.

The newline is supported which rocks. But is useless until it also supports the align* feature of the LaTex asmath module. Here's an example:

\begin{align*} 
2x - 5y &=  8 \\ 
3x + 9y &=  -12
\end{align*}

Which aligns where the & characters are.

Aligning a series of equations on an = sign is stock standard need in mathematical expression and work arounds with phantom and/or matrices are wholly inadequate. 

phantom works well enough if the LHS is unchanging.

matrix works well enough if you have time to kill in formatting and finding the right settings to space them right and are happy with ugly back code for your equations anulling one of the beauties of the current LaTex style support.