It's not just vertical tabs (which MS Edge has an option for), it's tree-structured vertical tabs. If you open a link in a new tab, the new tab will become a child of the original tab, making it easy to identify related groups of tabs. The subtrees can be expanded/collapsed. There are a lot of configurable options (e.g., to automatically collapse a subtree when you open a new one).
Minor addition: you have to create a user chrome file AND you have to go into about:config and set "toolkit.legacyUserProfileCustomizations.stylesheets" to true.
It means you can still read tab titles when you have more than a dozen tabs open. Plus you can nest and rearrange your tabs to fit your work or study.
For some, like me, it's a game changer and I dislike using chrome now because it doesn't support vertical tabs.
Caveat: to disable top-of-window tabs you have to use a user chrome CSS file, so it's not just "install extension, enable checkbox" easy.