I searched around a lot for this and the best solution for me works as mentioned in this detailed guide: http://tangledhelix.com/blog/2012/07/16/tmux-and-mouse-mode/

With the above approach implemented, you can copy from panes in a window as well by zooming into each pane first.

One important detail that was missing with the mouse mode is to press Shift before selecting an area to copy. This will copy it to traditional terminal buffer instead of the tmux copy buffer. (https://wiki.archlinux.org/index.php/Tmux#Scrolling_issues)

I searched around a lot for this and the best solution for me works as mentioned in this detailed guide: http://tangledhelix.com/blog/2012/07/16/tmux-and-mouse-mode/

Add these bindings in ~/.tmux.conf:

set -g mode-mouse on

unbind +
bind + \
  new-window -d -n tmux-zoom 'clear && echo TMUX ZOOM && read' \;\
  swap-pane -s tmux-zoom.0 \;\
  select-window -t tmux-zoom

unbind -
bind - \
  last-window \;\
  swap-pane -s tmux-zoom.0 \;\
  kill-window -t tmux-zoom

With the above approach implemented, you can copy from panes in a window as well by zooming into each pane first using Prefix +.

One important detail that was missing with the mouse mode is to press Shift before selecting an area to copy. This will copy it to traditional terminal buffer instead of the tmux copy buffer. (https://wiki.archlinux.org/index.php/Tmux#Scrolling_issues)