Menu item ellipses, style guide
Small cosmetic suggestion, but one I think is important to make Vivaldi a good macOS citizen:
Menu items on the Mac that lead to a dialog box typically have an ellipsis (...) after their name, such as "Save As..." because it opens a dialog box that requires further interaction. Compare this with a menu item that performs an action without further interaction such as "Close", which has no ellipsis following the word Close.
Here are a few menu items that should have an ellipsis after them, but currently don't. This is not a complete list and some of these items might be debated - see further below.
Check For Updates, Open File, Save Page As, Print, Export Bookmarks. Traditionally there hasn't been an ellipsis after "About Vivaldi" in the application menu. Please look at other macOS software for examples.
It's debatable whether or not "Print" or "Import Bookmarks and Settings" should have an ellipsis because they don't open conventional macOS-native dialog boxes. But hopefully from these examples (and please go look at other macOS software for examples) you'll see how it's traditionally done.
With the non-native dialog boxes it would be nice to stay consistent, regardless of which way you go with ellipsis versus no ellipsis.
Sorry to be picky, but I feel it's nice to stick to the conventions of the host operating system where possible and I don't think it would take much work to fix these up.