Mind your business.
Vertical tabs are a good feature for modern desktop monitors. I tried it on MS Edge and Brave Browser. I have Tree Style Tabs on Firefox, but the problem I have is the horizontal tab bar is difficult to remove if for it not that is make break something during an update. Not only that, but I use Nightly as my primary browser.
UBlock Origin — Wide spectrum ad blocker. https://addons.mozilla.org/en-US/firefox/addon/ublock-origin/
Tab Stash — Store tabs efficiently by using bookmarks. https://addons.mozilla.org/en-US/firefox/addon/tab-stash/
Web Archives – Save and look up archived web pages. https://addons.mozilla.org/en-US/firefox/addon/view-page-archive/
Bypass Paywalls — Access premium articles. https://github.com/bpc-clone/bypass-paywalls-firefox-clean
CopyTabTitleURL — Copy title & URL as a format with one copy. https://addons.mozilla.org/en-US/firefox/addon/copytabtitleurl/?utm_source=addons.mozilla.org&utm_medium=referral&utm_content=search
EPUB Reader — Read EPUB files within Firefox. https://addons.mozilla.org/en-US/firefox/addon/epubreader/ Read Aloud: A Text to Speech Voice Reader by LSD Software — It works with EPUB Reader. https://addons.mozilla.org/en-US/firefox/addon/read-aloud/
Default Bookmark Folder — Save bookmarks to a specific folder by typing, and the most relevant directories appear as you type. https://addons.mozilla.org/en-US/firefox/addon/default-bookmark-folder/
Gesturefy — Use gestures to navigate pages. Instead of looking for the back and forward buttons, just gesture with the mouse, left or right swiping motions. https://addons.mozilla.org/en-US/firefox/addon/gesturefy/
Swift Selection Search — Create right-click context menu searches. You can group searches together to output multiple queries at the same time, if you need that. https://addons.mozilla.org/en-US/firefox/addon/swift-selection-search/
Undo Close Tab — Pretty self-explanatory. https://addons.mozilla.org/en-US/firefox/addon/undoclosetabbutton/
TinyURL — Shorten long URLs with one click. https://addons.mozilla.org/en-US/firefox/addon/tiny_url/
SponsorBlock - Skip Sponsorships on YouTube — Watch YouTube videos and skip through all the sponsorships and promotions. https://addons.mozilla.org/en-US/firefox/addon/sponsorblock/
Bookmark search plus 2 — As the name implies. Very useful for large bookmark collections. https://addons.mozilla.org/en-US/firefox/addon/bookmark-search-plus-2/
Firefox Multi-Account Containers — Segregate your cookies for security reasons. https://addons.mozilla.org/en-US/firefox/addon/multi-account-containers/
Search Engines Helper — Create searches for your search bar or omnibar. https://addons.mozilla.org/en-US/firefox/addon/search-engines-helper/
Tree Style Tab — Organize your vertical tabs in their own hierarchy of trees. https://addons.mozilla.org/en-US/firefox/addon/tree-style-tab/