Don’t be sad. I’d say you’re doing it right! Vertical space is much more limited than horizontal on 21st century monitors, and tabs are wide, not tall. Tree tab UI enables semantic layout (showing you practically unlimited levels of nesting), plus they always give you consistent room to read page titles. Why should the usability of tabs decrease as you open more of them?
Don’t be sad. I’d say you’re doing it right! Vertical space is much more limited than horizontal on 21st century monitors, and tabs are wide, not tall. Tree tab UI enables semantic layout (showing you practically unlimited levels of nesting), plus they always give you consistent room to read page titles. Why should the usability of tabs decrease as you open more of them?