Access Vivaldi Settings
Windows and Linux: menu item Tools > Settings or the keyboard shortcut Alt P
Mac OS X: menu item Vivaldi > Preferences or the keyboard shortcut ⌘ ,
Settings are divided into sections. It is possible to display all settings at once by choosing Display All section located at the bottom of the list.
Search for the setting you want to modify by entering its term in the search field above the section list. Many settings will be applied immediately; however, if a restart of the browser for changes to be applied it will be denoted next to setting as applicable.
You can choose to open the Settings in a new tab instead of a separate window under Appearance > Window Appearance > Open Settings in a Tab.