OT: Just found out I can still add stocks if I use a different browser.
Having been a programmer in my past, I think Yahoo have underresourced the support in a misguided attempt to save money.
And why oh why don't they have a proper support function? All you can do is post your problem to a forum where a bunch of members of the public who know nothing make useless comments. Given there are dozens of posting complaining about the Add Symbol screwup, I wonder if anyone from Yahoo ever reads them.