- Edited
The choice between a horizontal tabbar at the top or tabs in a sidebar isn't really a global user preference to me. Placing tabs on the side or top depends on what I'm doing, case to case.
For example, if I have many tabs, I may want them on the side. If I want to "immersively" browser one or two sites in one window, I may want to tabs on top. When I'm developing with the dev tools on the right, I may also want to tabs on top to maximise the remaining horizontal space for the site.
I realise this would require a small (icon?) button in both states, but I imagine there may be more tab-related settings or actions coming in the future, so this could be a typical three dots ···
icon with all those secondary features grouped underneath.