Yes, you can simply edit the amount of shares, just like you said; not difficult at all. I agree, but that was not the point. The discussion was the option to record these sale transactions same as how you record transactions for additional shares you buy in a company.
Please re-read the whole sentence I wrote. I said it appears that you could record currency transactions in the Yahoo portfolio. I did not say it was with the Google portfolio.
This is what the option looks like to add the transaction in the Yahoo portfolio what I was actually talking about:
I don’t do currencies so cannot say for sure if it is the case or not. I simply highlighted the fact that the one vendor shows an ADD option where the other does not.