Get linux-workspacenumber where a tab is located?

[mabra]

The biggest problem for me is to restore browser sessions to its orignal linux-workspace. I am using wmctrl/xdotool to save all my browser-windows regularly (what helped me is, to give each browser a window-class).
But for restore, this cannot be perfect, because I am not getting the tab, but the title.
Is it possible using brotab to get the workspacenumber?
For this case, I could re-build my script around brotab.
Thanks!