It’s really frustrating that collapse/expand is a global setting, if I drag a tab out (a video for example) and want to collapse its sidebar to save space, I lose the sidebar on my main window as well.
I see there was a thread made in 2024 but it’s closed and locked now: Make 'closing the last open tab in a window' and 'closing the window' separate
I also submitted a GitHub ticket: https://github.com/brave/brave-browser/issues/49027