Are you talking about adding notes to calls in the call log?
I didn't even know that was possible, but I'm probably going to start using it as GV is my primary number for both personal and business. I don't think it is possible using the app (I couldn't find a way to do it).
The only solution I can think of is go to google voice on the browser and use desktop view. Not the best solution, but it works.
"Is life so dear, or peace so sweet, as to be purchased at the price of chains and slavery? Forbid it, Almighty God! I know not what course others may take; but as for me, give me liberty or give me death!"
-Patrick Henry, March 23, 1775