The new bookmark isn't added at the end of the folder (on the bookmarks page or bookmarks bar, I'm not using the bookmarks panel).
The bookmark pop-up doesn't remember the last chosen folder.
You have to double press Ctrl+D to access to the bookmark pop-up.
With the 4.0 version, the first and second points are no longer relevant. Nice!
@ghpy understandable given the trouble you have to get it working in the first place. I also had setup problems when the client was released as experimental preview end of last year, when M2 import was not even an option
I have used Opera M2 and Vivaldi side by side since, and found myself not requiring to use Opera12 for anything other than IRC anymore after little time. So opera now mainly is a first line of defense backup
So if you are using Vivaldi anyway as your browser, I suggest you just keep having it download your email too and you'll see when it becomes convenient.
As an end to this story:
I did not manage to get Vivaldi to import the mails from my 3 M2-accounts and work correctly afterwards. There was always at least one account not retrieving new mail or not showing imported mail. So in the end I deleted little used accounts from Opera and only imported mail from the remaining M2-account, adding the other two accounts to Vivaldi later without importing.
I recently troubleshooted a similar problem with upwork. Seems something on their end generates invalid persistent data sometimes and you just have to manually clear it. (I think it might just be overflowing?)
few features from a company that has "Theft" as a business model
(remove ads from sites needed set up by those folks that provide you content that you consume, and then make you watch their own ads instead so they earn the money instead of the content provider)
@odebroqueville sounds like bug VB-80288 which says that a german Umlaut in an imap folder (Gelöscht = Deleted) is displayed incorrectly, there the problem appeared in the deletion confirmation dialog.