Many important Vivaldi functions are available from the application menu.
Windows and Linux users can set the menu to either appear as a Vivaldi menu button or as a horizontal menu across the top of the window. Go to Settings > Appearance > Menu > Menu Position. Next to it you can also choose the menu icon style.
To edit, which commands and in which order are displayed in the browser application menu, go to Settings > Appearance > Menu > Menu customization.
For more detailed instructions, take a look at the help page about customizing Vivaldi menus.