Thanks for that, kgiii.
(You won't or at least shouldn't need sudo in your own home directory.)

No problem. Glad to have helped and no, you shouldn't need elevated permissions but I figured I'd mention it. I've been on a least privilege kick for a little while (I hang out on the AskUbuntu site a bit as well as StackExchange/Overflow and Unix) and it's kind of become a habit. I see people who will suggest stuff like sudo nano ~/bash_history and quietly edit it out. This stuff is meant to last forever, I guess.

Anyhow, I should write some sort of extension for this. It'd be nice if Opera opened up access to their sync servers. I'd then write an extension to sync the darned dictionary.

I use leafpad ~/.config/opera/"Custom Dictionary.txt" to edit. Quotes are required due to the space in the file name. Or... leafpad ~/.config/opera-beta/"Custom Dictionary.txt"

I suppose you probably already know all of this but someone might come along afterwards and not know. sighs It's that writing for AU that's made me do it! Who knows? The next person to come along might want to know. Hmm... You could probably alias it, if you used it often enough to warrant adding it to the list.

(You won't or at least shouldn't need sudo in your own home directory.)

/home/kgiii/.config/opera

Well, probably not "kgiii" for you but you get the idea. You can edit it without gksudo or sudo.

I use a lot of different computers and use cron to push a copy to my dropbox folder and then pull it down and it's automagically inserted into the appropriate folder ~/.config/opera (or beta, or dev).