when I use openoffice.org for math projects, I use OO.org formula to make formulas. but whet i look in applications >office> I can't find oo.org formula, how ever when i edit system>prefences>main menu I can edit it so i can find oo.org formula.

I have often to write chemical formulas, e.g.:

NH_4 Cl + H_2 O "<->" HCl + OH^"-" + NH_4 ^"+"

this arrow ("<->") should be like in this wiki-article:
Gleichgewichtspfeil

It would be extremly useful to implement this, because rightarrow or dlrarrow are not the same

edit: I don't want to replace any arrow. I want to add this arrow - and its not the same as the arrow for resonance (I'm sorry, couldn't find it in the english wiki):
"Dies wird durch den Mesomeriepfeil (Resonanzpfeil) ↔ symbolisiert, der nicht mit dem ein chemisches Gleichgewicht symbolisierenden Doppelpfeil \;\leftrightharpoons\; verwechselt werden darf." http://de.wikipedia.org/wiki/Mesomerie

means: the arrow for resonance may not be mixed up with the arrow for chemical equilibrium

To edit formulas is really difficult...
It would be really helpful, if you could edit the formulas like in MS Office.