Both Vivaldi and Edge have vertical tabs.

I really tried to switch to FF, but I need my vertical tabs, side-by-side/sidebar view and power user keyboard shortcuts.

I tried to use Tree Style Tabs, but that uses FF's sidebar view and I need the sidebar for other things too. There's a use case where I like to have two tabs open side by side, and the best way I found to do it in FF is the extension "Open in sidebar". But that overwrites the tree style tabs view, so I can either use vertical tabs or display websites in the sidebar, but not both at the same time! Not to mention that when I drag a tab out from a window, the website opened in the sidebar is carried over to the new window with it, which is infuriating! Also, Tree Style Tabs is so damn wide.

Another pet peeve is that searching in open tabs is not trivial. When you want to search in the titles of your open tabs with the goal of switching to it, you need to:

• Focus the address bar (e.g. Ctrl+L)
• Type % (Shift+5, Space)
• Write the name of the open tab and press Arrow Down and Enter to switch to it

Which is just too many steps for this use case to be efficient, and I do this a lot in other browsers!

Despite all the privacy problems and other issues, Edge:

• supports vertical tabs natively, with an option to only display a thin panel with only the tab favicons and display a wider view with the tab titles on hover
• has a sidebar view on the right that I can use to display my utility tab, and it can be used with vertical tabs active; or I can open two tabs side by side in one browser window
• when I drag a tab out or open a new browser window, the sidebar view is closed in the new window by default, which is what I want
• searching in open tabs and switching to them is as easy as a single hotkey to bring up the search, type name, press Enter

I like the idea of switching to FF and ditching Chromium very much, but these things are deal breakers for me and they're why I have to stay with Edge for now...

Orion does it now too.