.tmux.conf to create a pane layout at start - NB: launch it with `tmux attach`, and not plain `tmux`

.tmux-creating-panes-at-start.conf

# THIS IS THE PANE LAYOUT CREATED
# pane numbers are relative to the end of the actions
#  _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
# | pane 0        | pane 1         |
# |               |                |
# |               |- - - - - - - - |
# |               | pane 2         |
# |               |                |
# |               |- - - - - - - - |
# |               | pane 3         |
# |               |                |
# |               |- - - - - - - - |
# |               | pane 4         |
# |               |                |
# - - - - - - - - - - - - - - - - -

new -s my_sess # create new session
neww -n left # create new window
split-window -h -t left # create pane 0 (left) and pane 1 (to the right)
split-window -v # split pane 1 (current pane) in two --> new pane 2 on the bottom
split-window -v # split pane 2 (current pane) in two --> new pane 3 on the bottom
select-pane -t 1 # go back to upper right pane
split-window -v # split pane 1 (current pane) in two --> all pane numbers are shuffled

# additional commands I am actually not using (but they work!)
#split-window -v 'ls;bash -i' # same as above, but ls is executed in window
#select-pane -t 4 # go to lower right pane
#split-window -h # split pane 4 (current pane) in two horizontally

.tmux-with-commands-inside-panes.conf

new -s my_sess
neww -n left
split-window -h -t left 'cd ~/my-working-dir; npm run first-task' # pane will disappear if I CTRL-C the task
split-window -v 'cd ~/my-working-dir; npm start; bash -i' # because of "bash -i", pane won't disappear if I CTRL-C the task
split-window -v # no task running in this new pane
select-pane -t 1
split-window -v 'cd ~/my-working-dir; npm run another-task' # pane will disappear if I CTRL-C the task
# NB: DO NOT set remain-on-exit on ANYWHERE!!!

Could do something like bash -c "top;bash" to keep the pane open after quitting top. Or bash -c "while true; do top; done"