Current Design:
Here's a very basic konsole mock up, I used a solarized background otherwise it would be way too bland and most people do use it with a darker look.
I don't know if the tabs should extend the whole tab area or keep it as Breeze currently does. Edit: Full TAB is the way.
Some extra concepts:
The last two are concepts for tile identification and control.
The floating bars are pretty and cool looking, inspired by so many folks who run tiling managers with floating bars all over. Did I mention it looks cool.
Mock ups above updated on July 18th, 2020.