To improve the focus of your nested tmux you may hide the status bar.
Edit ~/.tmux.conf and add the following code and restart the tmux
# Toggle status bar visibility
bind b run-shell “tmux setw -g status $(tmux show -g -w status | grep -q off && echo on || echo off)”
bind b run-shell “tmux setw -g status $(tmux show -g -w status | grep -q off && echo on || echo off)”
Now you may use Prefix+b by default it should be ctrl+bb I did it b for bar, you may change it for your convenience.
