List hierarchically all window and panes in the input tmux session

tmux_list_all_panes.fish

# list all panes in the session specified in input
function tmux_list_all_panes
    if not set -q $argv
        echo $argv
            for el in (tmux list-windows -t $argv)
                echo "  "$el
                    for elem in (tmux list-pane -t $argv:(echo $el | cut -d":" -f 1))
                    echo "    "$elem
                end
            end
    else
        echo "Specify an input target session with -t NAME"
    end
end

# add completion to the previous function
complete -x -c tmux_list_all_panes -a '(tmux list-sessions | cut -d":" -f 1)'