Currently on Windows tab filtering / searching for open tabs continues to exist in the top chrome of the browser window (next to the application minimize, maximize, and close buttons). On Mac, when you switch to vertical tab mode the filtering /search function moves to the vertical tab side bar which is much more intuitive.
Please consider moving the tab filtering on the Brave Windows browser to the vertical tab sidebar to match the Mac experience.
Bonus, would be to simply make the filter/search a text input field instead of a button that you have to click in order to search for the tabs (since this becomes somewhat redundant).