I really like the sidebar, and I think vertical tabs are amazing, even though really new.
I want to make a lot of extensions like "side view" that open a website as a sidebar popup, for example a dictionary. This would be really useful.
But currently the vertical tabs are in the same sidebar, so a sidebar popup will be next to the sidebar, which is not ergonomic as it squeezes the main website to the very left. See this image:
Instead, 2 options would suffice for this:
1. Allow having the vertical tabs in a separate sidebar on the other side
With 2 sidebars this could then look like this. Tabs are one, sidebar is the other. I think this makes sense?
As the vertical tab bar does not have the default "sidebar spacer" this also looks really nice, not like 2 sidebars at all.
2. Allow addons to spawn a window on the other side
The popular (even recommended!) extension "SideBerry" is basically the same as the new vertical tabs UI-wise. It integrates nicely and works well, at least for now.
But with the new sidebar, Sideberry seems to use the "spawn popup window from sidebar" feature so it cannot be displayed at the same time as for example a "SideView" window would, which makes it a pretty bad tab bar. You would need to switch between them which is really bad UX.
So if Sideberry could spawn a separate popup on the opposite side, it would look like this:
Sideberry in this case would not be launched from the sidebar anymore but from an extension menu, or always shown. I am not sure how buggy that would be, for example the "overlay popup" or the "Orbit" extension covers part of the page and thus does not work at all.
So that popup would need to restrict the usable space to render websites, so that they adapt instead of being overlaid.
Regardless, any of those 2 features would be really nice! Until then I will stay with horizontal tabs which is kinda sad.
