Here's something neat!
Right-click on a Tab Stack and select the pin option from the context menu and free up the space an entire stack uses on the tab bar.
You can now pin Tab Stacks no matter how you prefer to use Tab Stacking - Whether open in Two-level Tab Stacks, Accordion style, or Compact.
Learn and enjoy our glorious tab features here
https://help.vivaldi.com/desktop/tabs/tab-features/