There’s many threads on this topic, none of them resolved (like Virtual Desktops and remembering the last state of the browser )
When you restart your PC, or sometimes just Brave itself, it ‘forgets’ what virtual desktop it’s windows were on, and gathers most of them on the first desktop, although it may, magically, leave one or two on the correct virtual desktop.
Furthermore, it will put some of the windows back in the right position (with previous sizing) and others will be rearranged and resized.
It is really that difficult to ‘follow the rules’ and keep track of the virtual desktop and coordinates of the open windows?