I don't believe there is a way to export accounts, however if you let RuneMate enter in the username and password, right after it has finished entering the username and right before it starts typing out the password, click on the username field and RuneMate will type the password there. You have to be quick or else it won't work, and as soon as RuneMate realises it has typed the password in the username field it will start backspacing to delete it.
That's much more clever than my solution. It has to exist in memory so I just scraped RuneMate running memory with cheatengine and was able to recover it just fine WHILE the handler was running. It doesn't appear to load into memory in clear text while the handler is inactive but I could just have been missing to too.
