[Libreoffice] How to add new commands for Math

Hi. I'm new here at LibO development.

I have interest on improve the Math component of LibreOffice by adding
some new commands into it: things like a wide inverted breve for
description of an arc between points A and B.

In order to do so, I've been looking & changing files with WideVec in
starmath module (files like starmath.h, commands.src, parse.cxx, etc).
Not successfully, though. My "wideibreve" attribute command isn't even
recognized as a command: its texts appears normally.

I know it's kinda vague, but any guides what I should do for add any
new command? And how to put it into the toolbox?

Regards,
Rodolfo