tmux.conf excerpt to toggle on/off session keybindings and prefix handling

toggle_keybindings.tmux.conf

bind -T root F12  \
  set prefix None \;\
  set key-table off \;\
  set status-style "fg=$color_status_text,bg=$color_window_off_status_bg" \;\
  set window-status-current-format "#[fg=$color_window_off_status_bg,bg=$color_window_off_status_current_bg]$separator_powerline_right#[default] #I:#W# #[fg=$color_window_off_status_current_bg,bg=$color_window_off_status_bg]$separator_powerline_right#[default]" \;\
  set window-status-current-style "fg=$color_dark,bold,bg=$color_window_off_status_current_bg" \;\
  if -F '#{pane_in_mode}' 'send-keys -X cancel' \;\
  refresh-client -S \;\

bind -T off F12 \
  set -u prefix \;\
  set -u key-table \;\
  set -u status-style \;\
  set -u window-status-current-style \;\
  set -u window-status-current-format \;\
  refresh-client -S
  
wg_is_keys_off="#[fg=$color_light,bg=$color_window_off_indicator]#([ $(tmux show-option -qv key-table) = 'off' ] && echo 'OFF')#[default]"

set -g status-right "$wg_is_keys_off #{sysstat_cpu} | #{sysstat_mem} | #{sysstat_loadavg} | $wg_user_host"

This is a minimal configuration for OFF mode (tmux 3.0a):
...
* using a different keybind to enable and disable OFF mode means you can now technically go arbitrarily deep with the TMUX nesting

It may be arbitrary, but it's not unlimited and we have to remember various keys.

Here is the true unlimited nested T-Mux:

### Nested T-Mux
bind-key        -T prefix   C-\\ \
    set-option      prefix none \;\
    set-option      key-table off \;\
    set-option      status-position top \;\
    set-option      status-style reverse \;\
    if-shell -F '#{pane_in_mode}' 'send-keys -X cancel'
bind-key        -T off      C-\\ \
    set-option      key-table on \;\
    set-option      status-style reverse,blink
bind-key        -T on       C-\\ \
    send-keys C-\\ \;\
    set-option      key-table off \;\
    set-option      status-style reverse,noblink
bind-key        -T on       C-Space \
    set-option -u   prefix \;\
    set-option -u   key-table \;\
    set-option      status-position bottom \;\
    set-option -u   status-style

I used on key-table, but it's actually pre-on, but it's just too long.

To send the get-out key (Ctrl+) to child T-Mux, just repeat it, and so on. So once the child T-Mux also enter the on key-table, now you have to press Ctrl+\ 4x to send it to the grand-child T-Mux. It can be laborious, however it can be unlimited and the status indicator hopefully help us point out which T-Mux sessions are in the on key-table.

The only caveats if you actually have local T-Mux of the same users nested (by hacking it via TMUX= tmux) as in this case you will create a new session of T-Mux (connected to the same server). In this case, the set-option key-table ... from any T-Mux sessions connected to the same server will affect their siblings in such whoever in the prefix mode will reset back to root. This may be T-Mux bug or unintended consequences as the command should only effect the "current" session, i.e. no -g option is given.

If different users start the T-Mux, then it's fine as each user will have their own T-Mux server. If you must do locally nested T-Mux with the same user, then you need to force it to start a different server, via -L or -S option.