So far so good. I took your advice and have installed the LastPass extension. Looks like I had already used it, as I already had an account with them, and many forum sites have their login info stored on my lastpass account.
Its not perfect--even though it has the login info, lastpass is still waiting for me to click on a button before entering the data. However, this only has to happen once. After clicking, and then loggin in, Opera's native password manager then asks if I want it to remember the login info. Over time, I willl gradually transfer these passwords into Opera, and then I won't have to worry about this any more.
Thanks for the recommendation. Its only 1 click per site extra, one time. After that, the passwords get automatically imported into Opera. That's a solution I can absolutely live with.