I use:

  - one top-level tmux
  - with a window for each workspace
  - running a nested tmuxsession, one per-
    workspace
  - for any codebase that can be indexed by
    cscope(1) I run cscope on window #0 of
    each nested tmux session, with
  - CSCOPE_EDITOR set to a script that
    launches $EDITOR in a new window in the
    same session, titled after the basename
    of the selected file
  - that CSCOPE_EDITOR script exits as soon
    it runs the `tmux new-window` command
    so that cscope gets focus back

This lets me use tmux+cscope as a poor-man's mouse-less IDE.