Both on Vivaldi on desktop and Vivaldi on Android, you have a few options for the location of newly opened tabs. To change where the new tab opens, go to Settings > Tabs > New Tab position either on desktop or Android. Then choose between the following options:

• After Related Tabs: The new tabs will share a “parent-child” relationship – if you open a link in your current tab, the new tab will open next to its “parent”.
• After Active Tab: Opens new tab next to the current active tab (this is the default).
• As Last Tab: Opens new tab at the end of the tabs.
• As Tab Stack With Related Tab: Opens a new tab stack with the active tab and the new tab.