This is not relevant for URL or search bars since they need to be displayed horizontally. Separate bars means less vertical screen space, which is still scarce.
My search bar is next to my URL bar, both are big enough and it has no impact on vertical space. I don't think I've seen any browsers where the two bars are stacked vertically.
In firefox preferences there still is an option to switch to old layout with two bars. Sadly it does exactly the same thing as adding search bar manually, that is gives you second redundant search bar and does not turn off search support in the original url bar.
Oh yes, I remember that. I don’t miss it at all, save for the annoying behavior of single bar when a search contains dot (e.g. searching for a dotnet namespace).
While the single bar is my preference I agree that more choice should be given to the end user. Google is trying to hard to shovel the changes that benefit them than addressing user’s needs (obvious example being AMP).
I've seen it, back around 1999, possibly konqueror? Something that let you drag around toolbars and if you moved the address bar to the left/right side it would change the direction of writing.
Let's say that testing it briefly was enough. Editing tilted text works up to around 45 degrees, steeper than that is a strain.
Good luck reading anything in latin script with a one-character wide vertical search bar. This would works for Chinese (that’s the traditional writing orientation) but definitely not for most other languages.
This is not relevant for URL or search bars since they need to be displayed horizontally. Separate bars means less vertical screen space, which is still scarce.